You haven't failed at all. The choices of your ex were beyond your control. What has always been in your control is, your actions.
This is your life, your story. How will you write the next chapter? Whether you realize it or not, you're currently in a relationship, with yourself. Don't neglect it. How hard are you willing to work to help yourself? Never stop asking for help when you need it, but do put in the same effort, if not more than your past relationship with the "other person" that didn't go as expected. If I were to make any suggestion, add mindfulness to your lifestyle. IMO, mindfulness will help you step out of your shoes, and simply observe what you're experiencing. It will help you understand emotions as they exist, and see things different than the perspective you currently have. This is important because, I have a different perspective than you, and from what I see, you're light years away from hopeless.
I'd also suggest adding any physical activity that has your true interest. You're clearly intelligent, and should understand the positive chemical effects it'll give you. Hell, start a community program at your shelter and meet some new bitches (dogs). Physically and mentally, occupy your time and don't let the past determine your present or future.
Anxiety. I'm afraid if you're experiencing it, then it's a part of you, for now. That's okay. It's more common than you think in our "modern world". Just don't let anxiety out of your sight, i.e. keep your enemies closer than your friends. Learn all you can about anxiety, and how it's affecting your life. Anxiety is a dated biological "feature" that helped us stay alive way back when, but these days just shows up to the party uninvited and ruins it. It's a party pooper, mostly. But hey, "every party needs a pooper".
In closing, your parents gifted you into this "magical" experience. Why not give it the old college try? After all, we're all in this together and at the end of the day, we're here for each other. Stay positive and never stop smiling.
"How ashamed I would be to let a day pass without making one more effort." - Isaac Asimov