Cancer is one of the most sensitive and intuitive signs out there. As a Water Sign, their emotions run deep, so whether you have your eyes set in one, or are already going out with one, there are a few things you should never do, and here's why:
Never criticize their family. This is the worst thing you could ever do to a Cancer. Nothing is more important to them and they will defend them fiercely, of course, right before dumping you.
Don't ignore your instincts. If your gut is telling you something about your relationship, listen. Cancer is by far the most intuitive sign, and they look for partners that are equally in touch with their emotions.
Don't force them to go out. If you had plans with a Cancer and all of sudden they end up canceling last minute, don't force them to come out. Cancer loves being home, especially after a rough day. A devoted partner, he or she will make it up to you.