Sex is supposed to be a pleasurable experience, but it's hard to feel sexy or intimate with your partner when you have sexual performance anxiety. When you're constantly wondering, "Am I doing this right?" "Is my partner enjoying this?" or "Do I look fat?" you become too preoccupied to enjoy sex.
Constant worry over your appearance or ability in bed can make sex stressful and nerve-wracking. It can even make you want to avoid having sex.
Sex is more than just a physical response. Arousal is tied into your emotions, too. When your mind is too stressed out to focus on sex, your body can't get excited either.