tl;dr You don't.
Even as a dedicated recreational player (10-20 hours a week) pretty much the only sane way to know for live is to review hands and see if you played them well, and even that is difficult because what basic theory suggests might be very different from what you should do vs. the old guy who has only limped for the past two hours or the drunk young kid playing every hand.
This will also screw up any long term analysis because even in a small room almost every session will have a significantly different mix of players in different positions, esp. depending on the time and day, so it's not like you are really playing the "same" game every time.
Then there will be problems like how you play on a Friday night after an annoying/tiring week at work, vs. turning up on a Saturday after being on vacation (you'll probably never get a good sample of either, and it'll be significantly different). Or what happens for the rest of the night after you drive an hour to play and the first hand you lose 100bb with AA vs. J6o.
You can also easily find results for significantly winning online players who had huge downswings over 20k hands, which would be about 18 months at 10 hours a week.
Worth mentioning again that basically all of the people who I'd consider semi-pros (30+ hours a week) at low stakes, table select aggressively, and aren't necessarily that great from a pure theory POV (being as kind as possible here).
About the best you can do is review every 100 or 200 hours and get hints at how well you are playing.
You probably also want to factor in how much it costs to get to the casino etc., and on the other side how much you are getting in comps.
Generic advice I see from higher stakes players is that you are crushing at +10bb an hour after a 2k hour sample.
Probably worth watching this:
https://www.youtube.com/watch?v=SOdJk7x9zHw