Show not tell “Happy”:

▪️Her cheeks glowed pink.

▪️He smiled, his brown eyes sparkling.

▪️She skipped across the room, humming a love song.

▪️He laid down with an amused smile on his face.

▪️Her hands clasped together and she squealed.

▪️She laughed, falling into the chair and holding her stomach.

▪️She jumped to her feet and cheered them on.

▪️She danced around her room, grinning wide.

▪️Her eyes teared with joy at the sight of her missing daughter.

▪️She wiggled her feet in the sheets, a soft sigh on her lips.

▪️Warm goosebumps broke out on her skin as she stared into his wonderful eyes.

▪️She waved her hands from side to side, twirling.

Notice that I’m not describing happy with “happy” synonyms: 

▪️She was ecstatic.

▪️She felt joyful.

▪️She looked cheery.

This is still telling and your readers won’t get the picture you’re trying to paint.

Example:

She felt so cheery and joyful. ✖️

Vs.

Her cheeks hurt from smiling as she skipped from the room, daydreaming and singing a love song. ✔️