Have you been in a slump working hard to force yourself to get back on track? By doing this you can create more pressure, tension, and anxiety for yourself, therefore intensifying the slump, making it deeper and longer.
Have you suffered an injury or injuries and you are having a hard time getting back on the court or field? Are you worried about re-injuring yourself?
Are you so worried about failure that you are distracted from your game and have a hard time staying focused?
Do you get angry at yourself or an unfair call during competition and take your mind out of the game affecting your ability to perform?
Do you worry about your opponent being better than you are?