Cancer is the reason that I don't believe?

I have been feeling very emotional lately (probably due to my recurring nightmares, but I won't get into that right now).  In short, I have been having trouble with my faith for the past couple of months, in the sense that I don't really believe in any god.  I believe in good morals--obviously--but I just do not believe that there is an outside force watching over what we do.  I don't believe in any sort of life after death.  When we die, we just die.  That's all there is to it.  Sometimes I like to pray despite these feelings, as a way to quell my fears for the time being. But is that worse than not believing?  Realizing that there is no god, but making one up anyway, so that life is more bearable? 

To get to the point, someone that is very dear to me has had cancer since before I can remember (since I was four to be exact).  This cancer has made me morally and spiritually stronger, but not necessarily religious stronger.  I always get really emotionally when I see someone with cancer, or something of the sort.  I hate it.  I hate it so much, but there is nothing I can do about it.  I feel so helpless, and watching the pain that it causes is more unbearable than suffering through it first hand. 

Ever since my first encounter with cancer, I have liked the idea of living in the present--the whole notion of carpe diem--but am not sure if a god resides in this present.  I believe that you have to be your own god.  Let me rephrase, I believe that you have to make the good in your life, despite all of the bad.  I am more than happy with the life I have been given, but I have an incessant sadness that resides inside of my subconscious.  I'm not depressed or anything, in fact, I'm quite the opposite.  I enjoy every day that I am given with the person, for I know that they could be taken from me in a different manner.  I have already been given 17 years with them, and hope that I may have 17 more.  Despite everything, I have been blessed with a truly wonderful life, whether it was by God--if there is a God--or by the luck of the draw.