I think I'm going to cancel my plans
Why are you cancelling plans?
I don't like the person and I'm tired of his shit.
It isn't very nice to cancel plans at the last minute.  However, it is also understandable if something bad caused the cancellation.
I don't care what you think.
Even so, I just want to let you know that plans are like a doctor's appointment. You always have to call in advance to cancel, so why not be courteous to your friend and do the same? Politeness goes miles, even if you don't like someone.