Its not so much when I think they're strong, its when I overthink things and conclude they're weak.

Example, I raise PF with AQ, get called, flop comes J66, I c-bet and he c/r's me. This looks like a really good place to bluff, so I assume he likely is. Cant remember if I called or if he was short and I just 3-bet enough to put him in and he called, but turns out he had AJ. Now just because it looked like a good place to bluff, doesnt mean at these stakes that villain really is bluffing here very often, and I should probably just give him credit even if I'm doubtful.