You’ll impose your own self-limits.
You won’t publish the blog post you just drafted up because you’re afraid of what others will think.
You won’t send the email you put together because the person probably won’t read it.
You won’t start the project you’ve been dreaming about because you’re worried it won’t work out.
Don’t worry, I do it too. We all do it.
Publish it anyway, send the email anyway, start the project anyway.*
*This doesn’t let you off the hook of putting your best effort in. It’s not an excuse to let work you’re not proud of out into the world. It’s permission to let go of the self-imposed limits you assign to yourself.