A word of advice to INFJs out there from a person who was clingy and obnoxious, a loser and nuisance and so on for several weeks this summer. In my defence I couldn't have helped it. I was under a lot of stress, really needed someone and a very polite INFJ just happened to be at the wrong place in the wrong time. If you don't envisage forming friendship with someone or helping them or catering to their needs - whatever those might be - and you can tell that this person, for whatever reason, is unable to figure out this unpleasant fact on their own, know that honesty and straightforwardness are the best policy. If you can, be gentle, but above all be clear about what you want or don't want.
This, probably, is a very unINFJ thing to do and it will hurt but you're doing yourself and this other person a favour. I suppose that for you INFJs this is the cross you have to bear. People cling to you just like (most) people feel awkward around INTJs.