To Bike or Not To Bike

I can't decide if/when to get back on my bike.

I took up road biking a few years ago. My brother-in-law became the head guy for the MS Society in our neck of the woods, and their biggest fund raiser is the MS150. Year 1, I didn't do anything but buy a cheap hybrid bike. Year 2, I trained for the event, but had a couple of bike accidents that prevented me from biking the event. Year 3, I was able to ride the entire first day of 75 miles. Year 4, I was able to complete all 150 miles (and got my Dx earlier that year).

But now I'm worried about going low while riding. Scares me to death.