Well if you're 99% sure, then go with it. But of course you're probably only right say 80% of the time even when you're 99% sure.

80% of 70% is still 56%
so if you're that sure, make the call
no matter what the pot size is
even if he has you beat, you can outdraw him
so you're going to win more than 60% of the time when you make that call