I'm not saying to disregard all the regular aspects of your
bet - native probability, reading cards, reading opponents, looking
at stacks, bluffing, etc. And yes, I realize that's the way the
pot got to $100 in the first place - by all that stuff going on
in the previous rounds.
It's your bet, and the pot is $100. I'm certainly not saying you
shouldn't employ all your best strategies at this point, only
that the $80 is a 'sunk cost' - it's not yours any more, it belongs
to the pot.
(unless, maybe, you're saying that getting a lot of your money into the pot is key to your strategy for the hand)
Am I making the distinction (hard to put into words)?