If you have no idea what the meaning of your life is, the following exercise can help you get started: make a list of reasons not to commit suicide.

This works best if you actually thought of committing suicide, i.e. it is not just a hypothetical "if I were to commit suicide, what would keep me from actually doing it?"

Follow up:

The first useful thing is that you can get a better picture of yourself by seeing what keeps you alive. Once you know that, you can improve yourself and do more of that stuff that brings you satisfaction. For instance, if your answer is "because I like reading books", it is obvious that you should read more books because you like the process; if you answer "because I can still do many good things for our society", then go ahead and do stuff for the society, etc). The point is that once you know what it is, do it! The entire world is better off if more people don't do what they don't like doing.

The second part of the experiment helps you learn more about your personality. For instance, someone stays alive to "read books" for their own pleasure; someone else wants to stay alive to make the lives of others better by "helping our society". Count the items in your list of reasons not to commit suicide, and establish your degree of altruism. You can establish degrees of anything else, as long as you know how to interpret the list.