Why?

Here is a quick test to perform on your workout:

Why are you doing those exercises? Why those reps? Why that many or that few sets? Why that much or that little rest?

You don't have to do all of them in one go. Try "why these exercises?" first. If you can't answer why, or your trainer can't...that's a problem. You have goals, right? Your exercises need to be a component of getting you there. Don't do things in the gym that don't lead to your destination.

For an example, let's do my workout from today. I have a strength coach, so I didn't choose my workout, but I understand the reasons for each component - because if I don't know I asked "why?"
Bench Press - there to develop maximal strength. Some back-off sets were done with a long pause on the chest, to work on keeping me tight at the bottom and to improve my ability to generate power from a dead stop. Why is that? I frequently have trouble with heavier bench presses because I get loose at the bottom. Dead-stop practice ensures I'm more skilled at dealing with that.
Lat Pulldown - with a wide grip on a thick bar. The thick bar is to help my grip strength for MMA. The wide overhand grip is to help develop my back's pulling power with minimal help from my arms.
Rickshaw Shrugs / DB "Power Cleans" - thick handled rickshaw shrugs to develop my neck/upper back strength and my grip all at once, plus DB "power cleans" to make sure my rear deltoids (the back part of the shoulder) gets sufficient exercise to grow stronger.
Kettlebell Snatch - to develop my power generation from the floor, and done with enough reps and short enough rest to develop some power-endurance (can I keep generating power as the workout - or my fight - goes on?).
Fat Bar Curls - to balance out the triceps exercises done earlier - bench pressing! Also a thick bar, for more grip work. Had I been doing underhand pulldowns or rows, you probably wouldn't see this - it wouldn't be needed!
Kettlebell Figure 8s - helps develop coordination, and the ability of my "core" (abs and lower back) to resist torque. Ability to generate and resist rotation is very useful in grappling sports.

All of the are there for a reason, nothing is thrown in just because. Nothing lacks a reason, and no "what do I need" lacks an exercise to cover it. Ab work? Figure eights did that. Pushing? Bench pressing. Pulling? Pulldowns and shrugs and cleans. Power endurance? Snatches. All-important grip work? Pretty much everything was thick-bar today to ensure a solid grip workout. It's all fun stuff to do, for me, but that's secondary. If I hated snatches I'd still have to do them, because...well, you know why.

So look at what you are doing and ask "Why?"