2014 PA State K-12 Scholastic Championship

After four rounds, I was the only perfect 4-0 player in the K-12 Open session.  I just needed a draw to secure the 1st place.  But I played too conservative, made an inaccurate move 42...Nc4? and threw the championship away.  Here is the last round game analyzed by Fritz.

[Event "PA State"] [Site "?"] [Date "2014.03.09"] [Round "5"] [White "LEON, ISAAC."] [Black "YANG, CHRISTOPHER."] [Result "1-0"] [ECO "E46"] [WhiteElo "2239"] [BlackElo "2209"] [Annotator "Fritz 13 (30s)"] [PlyCount "99"] {E46: Nimzo-Indian: Rubinstein: 4 e3 0-0 5 Ne2 without early Bd3} 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. e3 O-O 5. Nge2 d5 6. a3 Be7 7. cxd5 exd5 8. g3 a5 9. Bg2 Na6 10. O-O c6 11. f3 Nc7 12. e4 {last book move} b5 {Black has a new backward pawn: c6} 13. e5 {White threatens to win material: e5xf6} Nd7 14. f4 f5 {White has a new protected passed pawn: e5} 15. Qc2 Nb6 16. Nd1 Be6 {The black bishop is safe in front of e5} 17. Ne3 (17. Qxc6 $2 {is no good because of} Nc4 18. b3 Ra6 19. Qxa6 Nxa6 20. bxc4 dxc4 $17) 17... Qd7 18. Kh1 (18. g4 g6 19. gxf5 gxf5 $16) 18... Nc4 19. b3 Nxe3 20. Bxe3 Ra6 21. Nc1 a4 22. b4 Na8 23. Nd3 Nb6 24. Rad1 Ra7 25. Bf3 {White has an active position} Kh8 26. Qg2 Rg8 27. Bc1 Qe8 28. Be2 (28. Qe2 Nc4 $16) 28... Rc7 29. Ne1 Rf8 30. Nf3 Qc8 31. Kg1 Qd7 32. Kf2 { White king safety dropped} Ra8 (32... Nc4 33. Ne1 $14) 33. Ne1 Qe8 34. Rd3 Qf8 35. Nc2 Raa7 36. Ke1 Qc8 37. h3 Rab7 38. Kd1 Bf8 39. Rg1 Rf7 40. Rc3 Rbc7 41. Ne1 Qa8 42. Nf3 Nc4 $2 (42... Bc8 $142 $14 {would keep Black alive}) 43. Ng5 $18 Rfe7 44. Nxe6 Rxe6 45. g4 fxg4 (45... Rg6 46. Bd3 Rf7 47. Qf2 $18 (47. Bxf5 $6 Rxf5 48. Qh2 Bxb4 49. axb4 a3 $11)) 46. hxg4 $18 Qa7 47. Qf2 Kg8 (47... Re8 48. Rf3 $18) 48. Rf3 Re8 49. f5 Rce7 $6 {doesn't faze the opponent} (49... c5 50. Bxc4 dxc4 51. bxc5 Qb7 $18) 50. g5 1-0