How to? Convincing yourself it's not a lot of money as you move up

[napkins]

Accept the fact that you're playing for a lot of money. Don't lie to yourself, or try and convince yourself that it isn't that much. Instead, concentrate on the fact that poker is about decisions, and the corresponding money won/lost is a by-product of those decisions over the long run.

So, even if you lose a lot (but not a lot in proportion to your bankroll) you should be okay with the fact that you took a calculated risk that didn't happen to work out this time; but over the long run is a good decision if you're aiming to move up in stakes and become more profitable.