[microbet]

It's very natural to want to finish a winner. In SNGs it doesn't matter a lot, but in cash games quitting a winner and grinding it out when you are behind means in the long run you will spend the most time at the hardest tables. In SNGs it could possibly mean you will spend less time playing when you are at your best or less time during peak hours or something.

But, what citanul said is right too. If you are playing for fun, play when you feel like it.