1. Herculean Effort
At the end of your workout, if you are questioning your ability to make it through the same routine next time, you are probably taking on too much. You are either doing too many exercises, or performing them at an unsustainable intensity. Exercise should be challenging and enjoyable, not a battle to set a new world record each time out. Sure, events that test our overall conditioning are great from time to time and do a lot to benchmark progress. A good session at the gym should leave you feeling with a positive sense of accomplishment, and one on which we can build.
2. Marathon Training Sessions
If you feel pressured by the clock during exercise, you're either still overdoing things, or you're not focused on managing your time effectively. There's nothing worse than realizing that you've just spent 3-plus hours in the gym and wondering how you're going to keep finding that kind of time to make fitness work. This is when you should scrutinize your exercise plan and pare it down to what can be done in a manageable time-frame. I suggest at least 40 minutes and no more than 1 hour for most. Secondly, stay on task. Figure out how many sets you will do at each station and stick to a set time for rest between sets. For example, let's say 90 seconds of rest between each set. Keeping chit-chat and and smart phone distractions to a minimum will help, too.
Managing your routine and maintaining focus are very important, but often overlooked, steps in realizing short and long term goals.