... is doubt.
Whether you do something you've never done before, whether you do something that might not work out, or might be a little risky, doubt will always be the biggest productivity killer out there and ultimately hold you back.
So what can you do about that doubt?
You can't do anything about it...
All you can do is to decide.
To decide that you're going to do it.
That you're going to stick to that decision.
And that you're not going to let that voice inside your head stop your momentum.
If you're moving, keep going.
But make sure it's the right direction...