How does the meaning of life explain itself ?
Well, you have a fairly abstract question, and I suspect you intentionally stated it that way. In the strictest sense, life cannot explain itself, because life is experience. Therefore, WE are the ones who explain life based on the sum total of our experiences and understanding. I know, pretty abstract, right?
Some would also suggest that the meaning of life to one individual changes over time, and is supposed to. That is, there is no one answer to that question, rather, there are many answers, even for just one person, as his/her life changes over time, as do the circumstances under which it is lived.
Others have suggested that the important part is consistently reflecting on your life at various points, so that you can assess where you are at, where you think you should be, and what the "right" course of action is.