Perhaps this isn't as bad as I felt like it was in the moment, getting about ~30bb effective in here. This is a spot where I'm thinking through villain's range, and decide he probably has a set or a flush draw. I feel like a set is more likely, and I can't seem to find the discipline to fold. Maybe I'm being results oriented, but I need to get better at letting hands like these go I think. Any thoughts or tips on making big folds?

PokerStars - $10+$1|250/500 Ante 50.0 NL - Holdem - 9 players
Hand converted by PokerTracker 4

CO: 4,210 (VPIP: 10.00, PFR: 10.00, 3Bet Preflop: 0.00, Hands: 11)
BTN: 30,322 (VPIP: 0.00, PFR: 0.00, 3Bet Preflop: 0.00, Hands: 5)
SB: 25,255 (VPIP: 0.00, PFR: 0.00, 3Bet Preflop: 0.00, Hands: 11)
BB: 17,000 (VPIP: 25.00, PFR: 12.50, 3Bet Preflop: 50.00, Hands: 8)
Hero (UTG): 19,437
UTG+1: 11,585 (VPIP: 18.18, PFR: 9.09, 3Bet Preflop: 0.00, Hands: 11)
MP: 4,900 (VPIP: 0.00, PFR: 0.00, 3Bet Preflop: -, Hands: 2)
MP+1: 6,100 (VPIP: 50.00, PFR: 0.00, 3Bet Preflop: -, Hands: 2)
MP+2: 41,145 (VPIP: 45.45, PFR: 45.45, 3Bet Preflop: 33.33, Hands: 11)

9 players post ante of 50, SB posts SB 250, BB posts BB 500

Pre Flop: (pot: 1,200) Hero has  K K 

[color=red]Hero raises to 1,000[/color], fold, fold, MP+1 calls 1,000, fold, fold, fold, fold, BB calls 500

Flop: (3,700, 3 players)  9 5 3 
[color=red]BB bets 500[/color], [color=red]Hero raises to 3,333[/color], fold, [color=red]BB raises to 9,666[/color], [color=red]Hero raises to 18,387 and is all-in[/color], BB calls 6,284 and is all-in

Turn: (35,600, 2 players)  Q 

River: (35,600, 2 players)  T