But I really want to know what thought process you have to have to suck it up

I have no thought process to "suck it up". That is cause I don't think of her previous partners. Not once.

When I'm with someone new then I'm in the moment. It's me and her trying to make this as good as possible. Nobody is in the past .. No one cares about the past. We are here making this moment as good as possible and if that turns out great then we will look forward

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Some people say "treat her experience as a positive for you to learn" kinda thing helps

To me that is BS .. Her experience is hers. You can't learn from it .. You can benefit from it in that the fact she has been with other might make it easier for her to read you and make her a better match.

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You experience is what you learn from. I kinda suspect that you don't realize a lot of things about sex and partners.

Here one example:

You don't have sexual chemistry with every girl you met. With some girls sex will be awesome for the both of you the first time, while with other it is going to be pretty awful and will not improve no matter how many times you sleep together.