One of my biggest pert peeves is seeing trainers or websites providing workouts that have upwards of 10-20 exercises. It’s almost as if they think that by doing more exercises regardless of effectiveness they will get better results. Let’s apply that to our nutrition. You are hungry so you eat some candy. But you are still hungry so you eat some potato chips. Then some ice cream. You seem to never get satisfied. Whereas if you had eaten a full meal, rich in nutrients, vegetables, lean proteins and healthy fats then you would be more then satisfied.
Getting back to workouts, people do the same thing. Instead of choosing a small selection of effective exercises and performing them at the proper intensity until their body has reached its limits, they forget quality and go for quantity. If you are giving your full effort in a given exercise, say back squats, then after you complete your final rep you shouldn’t have the ability to do much more then a few accessory exercises and definitely not at your max effort.
The idea of “saving” energy for your next exercise is silly and not productive. Instead of saving energy, put all your effort in one exercise for that given body part. I’m going to bust out another analogy so bare with me. You and a friend are each driving a car through the desert. You are both low on fuel. You can combine your fuel together and arrive safely or continue on separately and end up dead in the desert. Putting all your energy into one goal is the only way to increase strength and make the most out of your workout.
A well known example of this is Jim Wendler’s 5-3-1 program. A very successful power lifter, he translated his program into one that anyone can use to drastically improve strength and muscle. He uses one heavy compound lift ie Deadlift, back squat, bench press or standing shoulder press per workout. He recommends 2 accessory exercises to build muscle but has no problem if time only allows for your main lift. Of course that one lift with challenge every fibre of your being.

I’ve put together an example of a workout that will increase strength and build muscle for a person with only 3 days a week to workout.

Day 1
Back Squats 4 sets of 6@65,70,75, 80%1RM with a drops set on the 4th. Set hitting all your percentages

Romanian BB Deadlifts 3×15
Weighted Crunches 3×20

100 push ups

Day 2
Bench Press 4×6@65,70,75,80 of 1RM with drop set at 4th set to exhaustion

Seated Cable Row 3×15
Standing DB press 3×15

100 sit ups

Day 3

Barbell Deadlifts 4×6@65,70,75 and 80% of 1RM with 4th set drop set

Bulgarian Split Squats 3×15 per leg
Reverse Hyper Extensions 3×15

50 chin ups

In a world of more is better, take a step back and simply the program for bigger results.