You won't "come back and finish", or at least it's very unlikely. Your brain will never be more plastic than it is right now. To echo the other comments here,

You won't "come back and finish", or at least it's very unlikely. Your brain will never be more plastic than it is right now. To echo the other comments here, what prevents you from working on your idea without dropping out? Is it the kind of project that requires 16 hour marathon hacking sessions every day for months on end?