Don’t…
...tell them you’ll text them later if you aren’t planning to.
“OK gtg but I’ll definitely text you later!” → instead, say, “I have a busy day but will try to text you later”
...be too abrupt.
“I’ll think about it, talk to you tomorrow” → instead, say, “Lemme think about it, k? Heading to class now but we’ll talk about it tomorrow.
“That sucks about your test, heading to bed now, later” → instead, say, “Ugh, that sucks :( I know you studied really hard for that, are you doing OK? I was about to head to bed but we can talk really fast if you want.”
...end on a negative note.
“Thought your presentation was OK but you did better when you were just practicing with me. Gotta go, see you in math” → instead, say, “Yeah I thought you did pretty well! Can’t talk now cause I’m heading to class, but we’ll talk more about it later ok?”
“Yeah, this day sucks. Talk to you later.” → “Today hasn’t been good so far… hopefully it gets better soon. Hope you’re doing well too. Talk to you tonight?”