How Far...

So back in like September my mom and I went to VA to visit my aunt who suffers from deppression. Driving back home my mom said to me you never know what it is that can break you. For my aunt it was her husband leaving her. Last night on the treadmill I was thinking about this. How far can I be pushed before I crack? The thought haunts me a bit. I have several family members that suffer from some form of mental illness or another and I've always felt a bit of pride that I'm so emotionally stable. I suppose at this point my greatest fear is losing that stability. The fear that no matter what, I'm doomed to go crazy.
For the most part I have made peace with my recent miscarriage, however, I have this lingering guilt b/c when I was five weeks pregnant (I was unaware I was pregnant) I took a spinning class and my baby died like a week later. I know there is no way of knowing if that is the cause, but a part of me wonders if I unwittingly killed my unborn child. A child I tried for 14months to conceive. Could I go through that all over again and still hold it together? Will I have to? I wonder if another baby will quell my guilt for this loss.
Crap. Now I feel like crying.
I think I'll get dressed and go to the gym.