People love to pick up on the codes from the signals we all put out, and in fiction it’s one of your strongest forms of reader participation. So the less you explain things to your readers, especially characters’ emotions, the more intense their involvement. There will be times when an explanation will be unavoidable or even desirable, but as a general rule, when you catch yourself explaining how a character feels, first see if the emotion can’t be discerned from what you’ve already written. If it can’t, try to find a way to make that possible.
Phrases like “I was terrified,” “He made me so nervous I could hardly speak,” and “My heart was beating so fast I was afraid she’d hear it,” show up with dismaying regularity in the fiction of novice writers.