75% of everything in parkour is getting over fear. That's the biggest hurdle there is.
I can't really tell you how to do that.
I can say just go do it, and you can get all hyped up and... then you bail instead of trying it.
The best thing I can tell you is to setup an environment where you feel comfortable failing (a lot).
If you have or can get a gymnastics mat, great. If you can convince yourself it's safe to fall on that, then you can get by a lot of the fear.
The fear still affects me a lot too. I often find myself saying "Yep, I am going to die. This is it." before doing stuff.
Just practice the heck out of the progression stuff and hope for the best.
I would suggest trying to get the side flip down first. It's like a parkour roll, just in the air.
Find a thing you can parkour roll over that is ideally at about the top of your core level and then jump and do a parkour roll over it and fall off the other side. Put something on top of it to make it softer and get the height where you want it to be if it's helpful.
Keep parkour rolling over that thing and doing it faster and faster. This should train your muscles to do what they need to do in a pretty safe way since you are supported the whole time.
After enough practice doing this, your muscles should hopefully be built up to the point that you can actually jump well higher than just the thing and you can try to make it over without touching it. If you fail, you still have this thing to catch you. Just practice the heck out of it.
If you can consistently get over it without touching it, there shouldn't be a reason to fear doing it anywhere.
