The inner critic — the voice that says you're not good enough, smart enough, ready enough — has been with most of us for so long that we have come to mistake it for truth. We treat its pronouncements as accurate assessments rather than what they actually are: a protection mechanism that has outlived its usefulness.
The inner critic was built to protect you. At some point in your development — usually early, usually in response to criticism or failure or social rejection — your mind decided that if it criticised you first and hardest, it could prepare you for the criticism of others. Better to know your own weaknesses before someone else names them. Better to expect failure than to be surprised by it.
This made sense at the time. It may have protected you from real harm. But it was designed for a specific set of circumstances that no longer fully apply, and it has generalised far beyond its original brief. It now critiques you in situations where the risk is minimal, the stakes are manageable, and the thing it's warning you away from is precisely the thing that would help you grow.
When you hear the critic — you can't do this, who do you think you are, you're going to fail — it is worth remembering: this voice is not neutral. It has an agenda. Its agenda is safety and smallness. And safety and smallness are not the same thing as a good life.
Thank it for its concern. Then do the thing anyway.