It also depends on the area of the risk. I try not to take risks with my health and other parts of life I can't control well enough to balance out later. Materialistic things come and go. Most people come and go. So, taking a risk in that is easier to manage.
If the chance of success is 50%, it doesn't mean the rate is that, too. As I mentioned, I'm pretty good in turning something into a success. Even if I end up on the loosing side, I can still make something out of it - at the least, a lessons learned.