In the years I have been a trainer I have found part of the reason people don’t stick to new workouts plans in the past is they think every workout has to push them to their limits and basically be miserable torture.
When I have a new client the first thing I tell them is they don’t need to be pushed that hard every single workout to see results, in fact sub-maximal training is where the most gains are actually made. Rather than training for a 1 rep max, or completing sets to failure, you actually want to stay within 70-90% of maximal effort. That is where the most progress can be made, and you’ll tend to not hate your workouts as much either so you’ll be more likely to stick to your training when you aren’t overly fatigued after every session. The reason for this is that maximal effort can be too much for the body to efficiently recover from, especially if your allostatic load is already high from stress, lack of sleep, juggling multiple responsibilities, etc.
Unless you’re on vacation with no other worries in your mind and all the time to sleep and eat the best meals ever, your body is not running on a full tank of gas but rather half a tank at best. So before you push yourself to the point of feeling sick to stomach during your next workout remember that less is more even in the world of fitness!