Q: How do you motivate yourself to overcome 'imposter syndrome'. I love design and am trying to make the leap toward going pro, but always feel I don't belong there."
Everyone feels imposter syndrome to some degree. So instead or worrying about it, instead try to focus on helping those who know less than you by teaching them what you do know. Nobody who is at a more advanced level than you cares what you do, as they're too busy paying attention to their own work.
Every day there are thousands of people around the world starting out on a path that you are already hundreds, if not thousands of steps ahead of them. By helping them out, you will start getting feedback on how useful your help has been. Not only is this great, but you will start to feel as if you've earned the right to be positioned as a bit of an expert.
The market dictates whether you deserve to be considered a pro or not, so stop worrying about others and focus on producing the best work you can and before you know it you'll have earned your place.