Someone you care about was not there for you during a time when you really needed them. Even though this may have been a long time ago, dear Cancer, you can't forget it or let it go. You value loyalty, and you are extremely loyal yourself, so it's not like you don't deserve to expect the same from others. However, the other party may not realize that they let you down. They may not have recognized that their presence was so important to you at the time. None of us is perfect. If you need to talk about it, talk about it. At least give the other party a chance to understand and explain. Communication is key, and you can be a master communicator. You can do this in a way that is gentle and loving, but also firm.