I've been working on a game engine of my own in XNA and I'm about 2 months in from 2 hours a day spent coding, and I'm almost to the point where my engine could handle a battle system - animation, maps, sprites, and a decent UI system are all in, along with decent tools to generate the content for the engine to load, but it's taken a lot of work to reach that point, and in no way is it in a state that can be called a game.
I can easily see it taking another 6 months to even reach a point where real content can be used and the various parts of the game I've designed be play tested. Chances are you're going to be working on your project alone until you have something to show for it, so you'll probably end up in a similar situation that I'm in now. By all means go for it, but it's not an easy ride, and you have to be committed to finishing the project 100% or it just won't happen, I know that from experience.
Fortunately indie games are a big thing lately, so if you make something decent enough, you'll definitely be successful, so by all means keep going (Plus making something that's successful is a great addition to a CV)