This is not just a useless cliche, but rather experience gathered from thousands of games. This is NBA, at any given night, any team can beat any one, champions included. At any given night, any player can shoot the light out. What differenciate star players from average players, is the ability to perform at a high consistency, EVEN when opposing team design their defensive schema against you.
Players get beat up every single night, they shouldn't be fragile glass figures with sentimental feelings all the time. Just go out to play your game and play hard, coz ultimately, everything is decided by your game.