It depends on some factors: was it on purpose? was it expected or did the person hurt my trust? Is it a close person or someone who I couldn't care less about?

My boyfriend is often reminding me that while I'm gaining a headache from it, the other person is not even close to be thinking of me, so I'm just wasting time and energy. But, generally, I'm not one to hold grudges or take things personally when there's no reason to.