I hate being practical or realistic.. What' s the fun in that? Isn't the airplane, impossible? It's literally a bent piece of metal flying the sky. But someone believed in an impossible idea. Believing in yourself is probably a talent that will take you further than any of your creative talents in this industry. If you truly believe you will be the next Hollywood or Broadway star, you're halfway there.
With that being said, there are rare times in life you should be realistic and practical. I don't like being practical, but I realize its value. So you want to audition for the lead for in Wicked, but you don't have any Broadway credits, an agent and you've never been trained....probably not going to happen. Or you want to book a series regular role and your resume is full of stage credits....probably not going to happen. Start with something you know you can book, then work your way up from there. You just graduated from college and don't have any professional credits? Or you don't have any acting credits al all? Start with a student film or short film by an indie film director. This way, you build a relationship and you build you resume at the same time. Soon you'll meet people who have bee in more high profile jobs and you will be on your way to becoming the next Broadway/Hollywood star you've always dreamed of. But remember you'll be ON YOUR WAY. Its a journey.
Love your life.