This leads you to look for another workout.
Your jacked friend recommends the workout responsible for his physique. However, it has only been a couple of weeks and you hate it.
Create a Workout Plan
#1 - What is your goal?This should be the first question you ask prior to designing any training program. Your goals should dictate the focus of your program.
Is there a body part you need to bring up? If so, that body part should be prioritized when designing your program.
Are you shooting for a performance-based goal? If so, your plan should focus on things that will make you as good as possible at that activity.
For example, if you are preparing for a powerlifting meet, having a day dedicated to arms is probably not in your best interest, nor is going on distance runs multiple times weekly. Instead, you are going to want to focus your training around getting very good at squatting, bench pressing and deadlifting heavy weights.
Similarly, if you want to step onstage in the bikini class pink dumbbells and cardio won't help you reach your goal. You are going to need to focus the bulk of your training on lifting heavy weights targeting body parts such as glutes, legs, back and shoulders which are emphasized in competition.
On the other hand, if your goal is to set a PR in your next half marathon, maxing your bench press weekly isn't necessary. In fact, you probably prioritize endurance exercise over weightlifting in your plan (however, you still should lift weights if you are an endurance athletes because it has been shown to improve performance in endurance athletes. 
Although some of you may be thinking this is common sense, I think it is a really good idea to remind yourself what your fitness goals are when designing a training program so that you can work towards them effectively.
#2 - What do you enjoy doing?Another question that I think is often overlooked when designing a training program is addressing what you enjoy doing.
I often find that if I give someone what in theory is the "best" program for them, but they do not enjoy it, they will not work as hard or stay as consistent and therefore not reach their goals. However, if we implement some of the things they enjoy along with what should help them to progress; they may enjoy the program more and therefore work harder.
For example, if you enjoy bro-pumping arms, but your goal is to be the best powerlifter you can be, adding in some extra arm assistance work beyond what would be necessary for your powerlifting goals may help you enjoy your time in the gym.
Along the same lines, if you really enjoy training with a "bro" split and simply do not enjoy doing something like the upper/lower or split that the evidence-based crowd commonly recommends, it may be in your best interest to find something that is a happy medium between the two. Something that allows you to train with more frequency, yet still isolate body parts in a way you enjoy in the gym. For example, a 5 day rotation of arms, legs, chest/shoulders, back, and off may be something you consider.
Similarly, if there is a lift you don't enjoy, use a similar alternative. Hate good mornings? Why not try a similar movement such as a straight leg deadlift, glute ham raise, weighted back extension, or hip thrust instead, especially if doing so is going to allow you to enjoy your workout and push harder.
Ultimately, if you can find something you enjoy doing in the gym, incorporate it into your plan and by doing so you train harder because you enjoy what you are doing in many cases you may see more progress so long as what you are adding does not detract from your goals.
#3 - How much flexibility do you prefer in the gym?Individuals can vary greatly in the amount of structure they prefer in their workouts.
Are you someone who likes to have every single detail (sets, reps, weight, rest period, tempo, etc.) programmed out for you or would the thought of that may you absolutely dread heading to the gym?
For those that enjoy every detail programmed out, feel free to do so; however, oftentimes, I find that there are some individuals who simple prefer having a bit more flexibility in the gym. Perhaps for this group, a good middle ground may be to have a programmed progression for their main movements with a number of lift options or a volume total for their assistance work.
Ultimately, if you look at the sheet of paper your plan is written on and dread going into the gym to do it, you likely aren't going to work as hard. Give yourself the amount of flexibility you need in your program to stay sane, yet also be sure to still have enough structure that you ensure that you are progressing over time.
#4 - What is your injury history?If you do not compete in a sport like powerlifting or Olympic weightlifting, there are no lifts you have to do in the gym to make progress.
The barbell back squat, barbell deadlift, and barbell bench press are great movements. However, if you have an injury that keeps you from being able to do them pain-free, you do not have to do them in order to make progress. With that being said, I would advise you to verify that your pain or injury is not caused by a technique flaw first prior to throwing a movement out completely.
Assuming that form is not the issue and there are simply movements that cause pain, you can always find a similar alternative.
Does your back hurt when you do a barbell back squat? My guess is that you will still be able to do things like single leg dumbbell loaded squatting and lunging movements, leg press, hack squat, leg extensions, and a number of other lower body movements without pain. You may even be able to still squat with lighter weight and higher reps.
Similarly, if your shoulder hurts when you do barbell bench press, you could try things like db bench, a hammer strength machine, using a neutral grip, floor pressing, lowering the weight, slowing down the tempo or any combination.
If a lift causes pain, don't do it. Find a similar alternative that you enjoy doing and continue progressing towards your goals.
#5 - What else is going on in your life?Oftentimes, individuals will attempt workouts that are far beyond what their schedule or recovery abilities will allow. This can lead to reduced consistency, less gains, and worst case an injury.
Do you work a physical job? If so, you may want to consider training with less volume so that you are able to recover.
Are you under a lot of stress and not getting enough sleep? If so, you may want to consider training with less volume because high levels of stress can actually impair recovery from workouts and reduce progress over time. 
Are you only able to realistically be in the gym 3 days per week? You can still make great progress so long as you don't set up a 5 day split for yourself.
In some cases, with clients who are not able to consistently get to the gym due to their hectic schedule, I may give them volume goals for the week. They can break this up based upon what works for their schedule that week.
One week they may do two longer workouts and the next it may be 4-5 shorter workouts. However, as long as they are getting their training volume in using a schedule that fits into their life they still make progress.
As you are setting up your plan, be sure you are also taking into account your real life schedule and other stressors in your life to ensure you are recovering and progressing towards your goals.
Take Home PointThere is an increasing amount of science on training programming and a number of different training variables. This has led to the creation of a number of highly effective programs.
However, it is also important that your plan in the gym be one that you enjoy, remain consistent with and is appropriate for your goals.
Ultimately, by doing a program that is enjoy you will most likely work harder and if you work harder doing something that is reasonable for your goals you will likely make more progress.