Your brain defaults to negative thoughts to keep you safe. It generates excuses when you try something new. Intentionally focus on positive reasons and your ability to succeed instead.
Our brain is just a protection mechanism. It will naturally go towards negative. When we say, I want to do this thing. If that thing is out of your comfort zone, your brain will come up with a laundry list of reasons why you shouldn't do it, why you can't do it, why you're not good enough. Your brain will do that because it's trying to protect you, to stay inside of your comfort zone. So we have to be very intentional about finding the positive in things, finding the reasons why we can do it, finding the reasons why we will succeed, all of that stuff.