I am constantly torn between not folding on river in a big pot heads up, and trusting my read which tells me I am beaten.

I am leading the whole way. A scare card comes that looks like it will fit villains draw, and now I have to decide wether to call one more bet.

I know in a big pot I should call regardless, but where do we draw the line. Maybe it's because lately I am always losing these pots that I am questioning it now. I know early on when I was running good I won a bunch of pots with crying calls. Since I don't want "luck" to dictate here I must ask where the magic line exists between trusting your read and folding vs. making the crying call.