That "official," grownup, professional state that you think established creatives are operating from ... it's exactly the same as what you call attempting, experimenting, learning, rehearsing, trying.
These states of development don't end so much as you just get tired of waiting for them to give way to some magically confident Other.
Your work is work -- it usually sucks a little bit more than you wish it did; paradoxically, nobody else notices nearly as much as you might fear; it's not yours anymore once you give it to the world; and it continues to get better no matter how, when, where, or at what point you accept that the only "official" or "professional" thing about it (that there will ever be) is the cycle of starting and finishing.
If by "finishing" you think feeling done, feeling you've arrived, feeling it's perfect ... that's all a myth.
Following through is everything -- and the only thing -- that counts.
And there is great joy to be found in it.
Keep making. Start putting it all out there now. Observe the feedback (with constructive detachment). Pick up your check (if you've got one coming to you). Push on.
As humble as the reality of the creative process may be, there is one thing (for sure) that is magical, miraculous, divine about it -- no one else on earth can manifest your vision.
Image credit h.koppdelaney via Creative Commons on Flickr