I was told I would never make it because I'm too short. Well, I'm still too short, but I've got 10 All-Star games, two World Series championships, and I'm a very happy and contented guy. It doesn't matter what your height is, it's what's in your heart.
While green-screen work, find a way to stay true to whatever it is that it takes to act a scene out, and make sure that you use your imagination as best as you possibly can, still stay loose, and still allow yourself the liberty of doing what you need to do as an actor, and then work within the confines of what is actually possible.