Why do you believe it just because you think it?
Rather than blindly accepting what pops into your mind, trying challenging the thoughts that hold you back? Ask a question which will force you to focus on the positive alternative.
What's the complete opposite of this?
What if what I'm worrying about never happens?
What if this worry is teaching me to be strong?
Is this way of thinking helpful?
You might be amazed how strong your mind is.
If only you would give it a chance to show you.