It's Only My Nerves

Been reading up on the next steps for my screenplay.  Yes I'm ahead of myself, but at the same time, it pays to develop long-term goals.  An agent is in my future.  Back in the day I chased publishers,  now I'm a mess .  Why?  It makes me nervous because this is new territory, and I want to run from it.  I'm scared of succeeding, and scared of failing.  Can I write another screenplay?   Is the current one good?   Why am I beating myself up?  I will never give up writing.  I might as well get used to the fact that I will expand my horizons, not as a curiosity, but as a serious craftsman.