In the constant battle of ‘showing vs telling’, describing your character’s emotions is one place that telling can sneak into your writing.
Think about the physical effects of emotions in order to show how your character is feeling.
Don’t say they are nervous - show them refusing food, or repeatedly going to the toilet. Show them tapping their feet, drumming their hands, pacing the room. Show them checking their watch over and over, playing with their hair, or biting their lip.
Don’t say they are sad - show them retreating to their bedroom, show them listening to sad songs, or not paying attention to the television in front of them. Show them hugging a pillow, hiding under the duvet, writing angsty poetry. Show them crying, wailing, shaking, rocking. Show them eating ice cream, chocolate, cake.
Don’t say they are excited - show them chattering away, jumping up and down, clapping their hands. Show them grinning, laughing, hugging their friends. Show them dancing, running in circles, doing cartwheels.
Don’t just tell your readers what your characters are feeling; show them the physical effects of the emotion - physical effects that your readers can relate to. It will make your characters more real, more animated, and it will bring your readers closer to them.