Tough spot:
3$ 9 player SNG: blind 25/50
Hero (1800): UTG with JJ, bet 125
Villain (3000): OTB, raise 425. Villain is aggressive, but 2 times i get to see his cards he had the goods. Two times he checked raise all-in, one time he had AA, one time AK on raggidy board. Also a card rack so far. I don't think he is solid though. My table image: I guess my image is tight so far.
Hero called. Flop comes: 829 rainbow.
Hero check. Villain bet 650.
This question has been asked probably a million times. I think its a 50/50 fold/shove here. I end up folding. Good or not?

If you're going to fold just do it preflop.
Personally I would 4bet shove preflop.
If you're going to call the 3bet, I would definitely either lead shove or check-shove that flop.
I really don't get the call-fold..

Imo 4b jam pre, but if u decide to flat, folding that flop is not an option. It would mean u need a set or better to continue, u're not getting the odds for that to flat pre.
If this was higher BI, folding pre isn't really an option as well, it'd mean u can only defend vs 3b with QQ+, so u can just raise an uber tight range or be super exploitable. Ppl in 3$ won't notice tho, so doesn't really matter here.

"Why is it hard to JJ"

Cause some ppl do funny things with it, like u :P

i don't know how to play JJ
Yeap, i think i did something not too smart. I call preflop to get that kind of flop and end up folding. pretty smart.

yea i would probably shove and leave it to poker god to decide who's best. but you did raise well enough pf so i guess its ul if you face him with AA/kk or any kind of set hands.

This is either a great flop or really bad one [no overcards to slow you down]. Either way I'm shoving on this board texture. You'v even noted that villain is aggressive and he probably bets his entire range when you check to him. He'll have QQ+ sometimes [18 combos] but I think he has AK/TTs [22 combos] enough to justify getting it in.
At this level lot of players spaz out with AK otf in 3bet pots when they don't connect.

Don't be too hard on yourself - we all make mistakes learning.

The important lesson to learn is a good thought process.

You can see now that calling a hand that will rarely improve, then folding on about the best flop you can hope for was not a good idea, but what you haven't mentioned or perhaps realised yet - is that its a great demonstration that you didn't have a plan.

Making mistakes feels bad, but really the only bad thing is if we don't learn from them - and often there's much more to be learned - like wider principles with much broader applications, than we at first think.
Often it's more comfortable to just acknowledge an error and not think too deep about why.
You say "I suck with JJ"
I say "you don't plan hands well".
Address this and your game will move on quickly.