I won't try to give you advice, partly because there are guys here who already have, or could, who also happen to know a gazillion times more about all this than I do.
But what I can do, and will, is offer an anecdote...
What I've found to be the case (and I've only just recently fully realised this!
) is that when I'm very tired, or highly stressed (or have been within the last 24-48 hours, say), or when I haven't eaten enough (and yeah, sometimes it's difficult to get to grips with this, when you're not used to eating "a lot" - I know!) then the chances are, I'm going to feel weak, or the weights are going to feel heavier than they normally would, etc.
Likewise, when I - for a while - ate a lot less protein per day. Not good.
So, that pretty much just echoes/confirms what BtB posted upthread (surprise!
) but it is genuinely what I have discovered, with an open mind, as I always try to have.