For me, it is myself and the realization that I am in control of my own life. I have the power to be happy, no matter what the circumstances. This is my strength. When feeling down, like my life is out of control, I take the time to appreciate as many things in my life as I can. It doesn't matter how small, or how big. From the pillows on my bed to the dearest of my friends. I look at all the positives in my life.
Again, You are the creator of your own Universe. The choices you make in life are Yours. If you don't want to feel weak and apprehensive, then don't. Choose not to feel that way and feel appreciative for all of the good in your life instead.
When you concentrate on the good stuff and not the bad stuff, you bring more good things into your life. Try it. =]