how to text more “casually”?

people say i text too formally because i usually use grammar, punctuation, and paragraphs. they think i don't feel comfortable with them bc of that?? i hate texting so much, it gives me more anxiety then in-person conversations, but if i don't i won't be able to keep long-term friendships, especially during the summer when everyone is away. i've picked up on a couple of things, apparently periods give the impression you're angry or super serious, and in certain scenarios exclamation marks show that you don't feel super comfortable with someone? please give me more advice