your stack size is close to average so you are not in a desperate situation, and their stack size is not desperate either so the range would be ... likely - they have you dominated (aq,ak,aa) or strong advantage (qqkk) or 55/45 small villian advantage and ..... least likely - you have them dominated. seems like a fold to me. you say the hand cost you a lot but u don't say if it was becuz you called and lost or folded and would have won. either way if u fold here and see the hand play out that you would have won, that's the way it goes sometimes, when you have a decent stack going, you shouldn't make plays wondering about coulda shoulda woulda imo.
if you have a strong read on this player that u r likely way ahead preflop here, of course you have to discard all previous reasoning, and go with that, but even against these types I throw away hands sometimes because even loose agros do get hands. you never know when fortune may favor shortly down the road with a better opportunity, and so when u have a stack to work with that is usually the better option. either way you are depending a large part on luck, and luck is more likely to favor you waiting then going here i think. 21k with 400/800 blinds, i would consider that a stack to work with still, tho u r approaching moving time pretty quick, and here you a have a table round of free hands comin up after folding this one.
edit: everything i wrote above was based on the guy shoving has 36k stack. i realize now maybe i cant read that pic, the numbers too small. maybe it is only a 6k stack pushing? not sure