If you're over 21, you're an adult—like it or not. That means you are responsible for everything you say and do, and you are in charge of yourself and your life. Love is one of the areas of life where many of us have trouble remembering that we are adults, with responsibility.
Often, people react to the idea of responsibility as they would to the words “fault” or "blame"; as though saying “you're responsible for your life” means “you should feel guilty about your life.” This sense of responsibility is childlike. It reacts and responds as though an angry parent were standing over you saying "Who's responsible for this mess?".
Adult responsibility is something else altogether. It is really response-ability; that is, the ability to respond to life. Rather than placing blame, this way of thinking acknowledges personal power. Response-ability is the capacity to choose. Out of many possible responses, I can always choose the one I make. Response-ability is remembering to be in charge and make careful, thought-out choices.
What seems hard at first for most of my clients is understanding the need to take this kind of responsibility. The expression “taking responsibility” is ironically misleading, because actually we have no choice. We are always responding to situations, even if our response is to do nothing. It does little good to worry about what other people are choosing, because you really haven't any say about it. Your responsibility is to take care of yourself; no one else can do that for you.
When you respond with the best of your ability, and accept and handle whatever consequences you have helped to create, you not only benefit from your choices, but your life and relationships will improve immensely.