Are short term feelings holding you back?
One certain way to spin your wheels in relation to body composition goals is to focus on acute physiological feelings. ~ sweating ~ panting ~ heart rate ~ lying in a heap ~ getting a sik pump brah ~ DOMS ~ jelly legs etc. All come to mind. Don't get me wrong, there is nothing inherently wrong with these things. But they are not something that are set in stone. Maybe there is a smarter way?
What is the main component of physiological improvement? Simple, non-sexy answer... "Progression". Overload a muscle with as little as a few kilos more than the last time, you are pushing your body to adapt = improve = get stronger = faster = bigger etc. This is what equals physique improvements over days, months, years!
My mistakes: It isn't safe to overload every session (with or without the use of enhancement) you could injure yourself very quickly, further setting yourself back. I have learned the hard way... A few times! Listen to your body and if you feel ready to push for that extra few kg's or reps - go for it. If your technique is starting to deviate by as much as 10-15%.. Check the ego - leave it for another day!
Take home: don't get overly focused on short term fellings, it's much more important to progress than it is to feel tired!
*Disclaimer* This is not an excuse to train easy!