Chess is a finely balanced game. During the early opening, one can seldom deploy sufficient force to stop one's opponent from building a balanced position of defense and attack. Nevertheless, tension gradually builds into the middlegame. In most games, eventually, the tension will overbear a defense's ability to resist.
However, the balance is subtle. Defense does indeed often prosper for a while, which is why players tend to prefer early moves that both defend and attack. Nevertheless, middlegames can suddenly explode defenses and, even when middlegames do not explode, they do tend to erode defenses bit by bit.
Consider: pieces are exchanged, leaving defensive squares one can no longer cover. Pawns too are exchanged, exposing both positions to attacks that are more direct. Opening balance can be a good feeling but you can't hold it. Not quite.
And this is part of the mystique of chess, isn't it?
Therefore, you want a slightly different feeling in chess. Defend, surely. Seek opening balance to a point, but, as the middlegame emerges, recognize when the time has come to discharge one's own balance via an attack that disrupts the opponent's balance. Experience suggests that this is the sort of approach that chess most often rewards.
Much of chess is in knowing when to commit to the attack. Not too late.
A fairly rare exception exists. Occasionally, diagonal chains of pawns will interlock in the center, particularly in games that begin 1. d4. The interlock can force play out onto the wings. If the interlock forces both players out onto the same wing, then a type of position can arise in which some or all of the heavy pieces have been exchanged and in which the knights and bishops, which remain, are more effective in defense than attack.
But you won't see many games like this.
Here is an example of the more common kind of game, a game in which, recognizing that defense cannot indefinitely hold, the opponents discharge the tension and commit to the attack. (Black is a strong grandmaster. White is a onetime world champion.)
[title "V. Kramnik v. M. V. Krasenkow, Corus 2003"]
1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. c3 Nf6 5. d3 a6 6. Bb3 O-O 7. O-O d5 8. exd5 Nxd5 9. h3 Nb6 10. Re1 h6 11. Nbd2 Qxd3 12. Nxe5 Qg3 13. Qf3 Qxf3 14. Ndxf3 Ne7 15. Nd3 Bd6 16. Bf4 Ng6 17. Bxd6 cxd6 18. Re4 a5 19. Rd4 Rd8 20. Rd1 d5 21. Nc5 Ne7 22. a4 Re8 23. R4d2 Nd7 24. Nxd7 Bxd7 25. c4 dxc4 26. Rxd7 cxb3 27. Rxb7 Rab8 28. Rdd7 Nc6 29. Rxf7 Rxb7 30. Rxb7 Re4 31. Rxb3 Rxa4 32. Rb6 Rc4 33. g3 a4 34. h4 Nd4 35. Ne5 Rc5 36. Rb8+ Kh7 37. Nd7 Rb5 38. Ra8 Ne2+ 39. Kg2 Rxb2 40. h5 Nc3 41. Ne5 Rb5 42. f4 Ne4 43. g4 Nf6 44. Ng6 Ng8 45. Nf8+ Kh8 46. Ng6+ Kh7 47. Kf3 Rb3+ 48. Ke4 a3 49. Nf8+ Kh8 50. Ng6+ Kh7 51. g5 hxg5 52. fxg5 Rb4+ 53. Kf5 Rb5+ 54. Kg4 Rb4+ 55. Kf5 Rb5+ 56. Kg4 Rb4+ 57. Nf4 a2 58. Rxa2 Ne7 59. Ra8 Ng8 60. Ra7 Kh8 61. Ra8 Kh7 62. Rf8 Kh8 63. Kf3 Rb3+ 64. Ke4 Rb4+ 65. Ke5 Rb5+ 66. Nd5 Ra5 67. Rd8 Kh7 68. g6+ Kh8 69. h6 Ra7 70. Ne3 gxh6 71. Nf5 Ra5+ 72. Kf4 Ra4+ 73. Kf3 Ra3+ 74. Kg4 Ra4+ 75. Kh5 Ra7 76. Rf8 Rb7 77. Kh4 Rb4+ 78. Kg3 Rb6 79. Ne7 Kg7 80. Rf7+ 1-0