My friends asked me to wait here for them but I'd rather just leave.
Why do you want to leave?
I've waited long enough.
Feeling like you've waited long enough is understandable but if they asked you to wait here you shouldn't just leave. At the very least let them know that you're leaving and they might hurry up with what they're doing.
Fuck it, I'm going.
Give them a bit more time, or at least contact them. It is rude to agree to wait and then leave without saying anything.