You probably will not like what I have to say.
You need to stop being so aware of that person, and more aware of yourself. It's how we perceive others that helps or hurts them - and you!
For example, does your person have a lack of self control? Have you exhausted yourself trying to get them to behave differently? Acknowledge you can't do anything about it but change how you respond to their actions.
Good luck remembering this. If it was easy, the whole world would be getting along much better!