Old Dog, New Tricks

I am venturing on a new career of sorts and it's scaring the hell out of me. I've been messing around the whole "sales" concept forever - always being in the sales support position but have managed to avoid becoming the actual sales part; until now. I have always been good at the customer service/relationship parts but was comfortable in just collecting my monthly salary and not trying to live on commission. The thought is making me ill. I have so many people around me who are supporting me and my success but what if I fail? What if I can't cut it and there is no business for the commissions? How long do I wait? How long do I try? I know, from my previous experiences, it takes about two years to build up a clientele and become fairly successful. I don't have two years. One deal a month and I'm happy but what if I fail? Urghhhh.... I am trying to be positive but inside? I'm terrified of failure.