Having a hard time believing that having 20% conversion rate is possible

I have set a goal and I will be able to achieve it if I have 10-20% conversion rate. However, my last launch had less than 1% conversion rate and I find it soooo hard to believe having 10-20% conversion rate is even possible.

I am now changing my strategy completely and intellectually I know now 10-20% conversion rate is possible. However, I find it so hard to believe that. How can I practicing in believing this?

I have tried to find reasons of why this could be true but I am always just believing intellectually and not really believing deep down in it.