Good surprise: there's some totally bogus mental shit that quiets down. I had always told myself "I wish I could afford [expensive musical instrument], I would love to play that", with the implication of "poor me..." Probably had that thought once a week. Suddenly I had enough money to buy one a week if I wanted to, realized if I had really wanted it I totally could have years earlier, and that it just wasn't that important to me - it was just a pity party. That voice quieted down and life got easier for it.

Bad surprise: there's a bunch of people you absolutely should not expose your means to, including that you donated money to something - they'll resent you seemingly no matter what you do. Example: a big multi-year capital project at my kid's public high school was at $67K out of a $75K goal and been stuck there for a almost a year. I had had a good year, and quietly contacted the director and kicked in the last $7,500 so the organization could move on to other projects. Asked them not to make a big deal about it but didn't formally request anonymity. There was no public announcement and no dedication ceremony but they put our name on the plaque and word got out we'd finished it off. Half the other parents in the organization gave us side-eye for the next year and we didn't get invited to some stuff anymore. WTF?

Unsolicited advice, read "Your Money or Your Life", which will not only help you accumulate but also not f*** it up if you succeed.