You may not want to accept it, but what you are is of your own making. Not in the "you're the master of your own destiny" sense, but in the sense that your past actions (perhaps not in this lifetime) have put you in the position that you currently are in, be it good or bad. To be sure, there are other forces that are at play too, but the strong believer in the law of Karma that I am, I can't but think that the presence or absence of even those forces are influenced by your actions.
Say you're going through a tough time in life. It may be someone who's just making your life miserable at your workplace; or it may be a real big problem in your personal life. You can be sure that there's something you have done in your past, perhaps not to the same people who are currently causing your problems, but some others. Contrary to popular belief, I feel that life is always fair, and we get what we deserve eventually, one way or the other.
That doesn't mean that we need to be fatalists who will do nothing to improve their own state of affairs, and bemoan the fact that fate has chosen them for her victims. No, not at all. You ought to do what's in your power - to the limits of your code of ethics - to pull yourself out of your current, undesirable state. Finding excuses for wallowing in self-pity is most certainly not what I'm advocating.
However, if you finally find yourself defeated in your pursuits, either by a human agent, or by an unkind Providence, the thought that what happened to you was nothing more and nothing less than what you rightfully deserved, may help in reconciling yourself to the defeat, and getting on with the rest of your life. In other words, it could serve as a resting point in the long and often tiresome journey of life; a theory that will kick in and explain events when other theories fail.
But - make no mistake about this - your pain will entirely be your cross to bear!