We've all seen the threads about a new hit game made by a new programmer that will be better than commercial titles. These 'newbies', as most call them, need a little help to correct their path.
Here is what I do:
Imagine a glass jar (you). Now imagine that a grenade (near-impossible ideas) is stuck in the jar. The only way to keep the grenade from going off is the surpress the will to start big, think realistically, practice your skills, and try to gain experience. Just follow everyone's advice, only ask specific, descriptive, and relevant questions when you have trouble, be polite, and never let discouragement and obstacles get the best of you. Start off small and gradually build on what you learn. You will eventually be able to make an online RPG or what have you, it just requires practice, determination, and experience, things that are possible to aquire.
Hope that helps you out.