What is the best approach to handle "bad days" ?

I have "bad days" - meaning I can't lift as much as usual, and not for as long as a normal session.
So far I can't link it to a particular cause ( it's not sleep, it's not food, it's not low sugar or dehydratation). Not sure this happens only to me or if it's a common occurrence I haven't found anything about that in the FAQ).
Anyway, what is the best approach : Train with lower weights for a shorter time, or just go home and go the next day instead ?


Answers:

Could be recovery, (or lack of complete recovery), your body fighting something off or other unidentified stressors. Best advice my trainer gave me for these situations: do the major lifts as best as you can (at the weight you can that day) and save it. On a really bad day, just walk away and come back tomorrow. Don't let it get to you, as another poster said it is a marathon, not a sprint!

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Its just a bad day, try to not let it get to you. Look at it from larger perspective than a day to day basis. When you start thinking about it in years then its no longer a big deal to have a bad day (or even a bad week). I am no way good at this myself, I try my very hardest tho.