If you want to make the move from writing as a hobby to writing as a profession, you need to act, well, professionally. Right now. Not 'when you've made it' or 'when you hear back from Agent X' or, even, 'one day'.
If you are serious about getting published (whether traditionally or by going it alone), you have to make a plan and the very first item on that list should be 'fake it until you make it'. Or words to that effect, at any rate.
What do I mean by acting professionally? Well, imagine you make your living by writing and publishing books. Imagine that the publishing professionals you wish to work with (now and in the future) and every potential reader of your work are watching your every move. They're not, of course, but the point is that they could be.
Do you have a blog? Wonderful. Does it have a clean, professional design and a clear focus? Is the writing error-free and a reflection of the public persona you wish to project?
Do you have a contact form or your email address on your contact page?
Are you on Twitter or Facebook or Tumblr? Are these profiles linked to your 'writing' persona and, if so, are they appropriate? You don't have to pretend to be a different person, but you should always conduct yourself online as your 'best' self.
If your online presence is littered with bile-filled rants against the publishing industry, literary agents, or even books, you might want to consider the impression you are giving the industry you wish to join. It's like publicly bad-mouthing the company you have just applied to, the morning of your first interview.
I would also recommend that you rid yourself of any 'us and them' ideas you may have and distance yourself from those who spout them. It always amazes me how vitriolic and bitter some aspiring writers can be about the so-called 'gate keepers'. Agents and editors make decisions about manuscripts based on whether they think they can sell them and whether they feel sufficiently passionate about the writing to go and take the chance.
Keep your professional hat firmly on during the submission process and remember that you are trying to find a good fit for a mutually beneficial business relationship. It's not personal! (In my experience, it can help to chant that while drinking wine and eating chocolate).