Well, probably not nothing. It’s likely some amount of fear, which can mean there are actual risks involved with whatever it is you’re considering.
Or maybe you’re being held back by actual constraints like legal restrictions.
Perhaps you’re facing systemic inequality which makes it exponentially harder for you to gain the required access or resources than for most people.
It could be that you’ve already committed the necessary resources to some other pursuit, and your prior choice made this other goal less of a priority.
Maybe you still need to develop some necessary skills before pursuing your goal.
Maybe you are in some way incapable. We can’t all do everything.
Maybe deep down inside, you don’t really want to do this.
Or maybe there’s nothing stopping you, and all you needed was a lovely picture of some mountains to remind you of that.