All relationships go through ups and downs. They may last days, weeks, or even months; but if the relationship is generally good, it's worth hanging in there through the hardships. There are cases, however, when it's just time to move on. It will be better for both of you in the long run despite the pain now.
How do you know, though? Sometimes it's like hanging a picture: you're just too close to the artwork to realize it is crooked. Before you call a relationship psychic, check here to see if your relationship is exhibiting some of the major warning signs.