Coming back from a Serious Injury
That's rough. Rotten luck and you have my sympathy. 

When you say "as a kid" am I right to think not fully grown? Because little kids start closer to the ground, don't weigh as much, and don't tend to be going as fast, but crash a lot. Teenagers are a different matter: good reactions but poor judgement and the size and speed of adults, but they're quick to heal and fractures tend to be less severe as their bones are more flexible. 

Did you by any chance suffer any kind of hand injury? Apparently breaking the clavicle is common coming off a bike if you put your hand down, but that's instinctive (I was lucky recently that I was still holding the flat bars when I hit the ground, and was a lot slower).

You may never know exactly why you came off this time (why you got to the grass in the first place). Maybe you were pushing your speed right to the limit of the grip on a bend and hit a bad bit of road, or instinctively dodged something. Maybe you were very close and the wind shifted. Maybe tiredness contributed. Trying to hop back onto the road was a bold move that I couldn't carry off, but many people could and you know your own skills. Maybe it would have worked but for continuing bad luck.

When you get back on the bike, you'll have to build up gradually. You won't be as fast, as flexible, or as fit (even if the medics allow you to do some trainer work as part of your recovery - you may even be encouraged to at the later stages but). Go out with a group, but a slower one, and people you trust not to push you too hard until you're ready - buddies are great for confidence. Start with decent riding conditions - if you're in the Northern hemisphere that's easy as you'll be out in the summer. Know that you've got to look after yourself. And see a good physio, preferably one who specialises in injured athletes. 

Right now you're not in a good place, but as you get back out and ride you'll be able to make a full recovery from the mental as well as the physical trauma.