I was timid about starting mountain biking because of crashing and you may do it. But once you get a grip on the basic skills you will likely not fall. It is really fun and although at times frustrating it is a really awesome feeling to keep progressing. Finding a group or clinic you feel comfortable in reaching out of your comfort zone can really teach you a lot. I learned so much once I found one and found a discipline I love plus an amazing group of friends.