Why now? Why, when I seem to be doing so good in life, do I suffer from this crippling anxiety now?

Asking why someone has anxiety when they have nothing to be anxious about or their life is going well is like asking why asthmatic people are struggling to breathe when they're surrounded by perfectly good air. Conditions don't adapt to circumstances

Anxiety can strike anywhere at anyone at anytime. Unfortunately it can be the anxiety is caused by a lingering fear of loss or failure. Do you think there are ways to assuage that potential feeling?

Anxiety is sometime difficult to cope with, and its even worse whenever something good in life is going on. What's caused this for you?

Anxiety has no agenda, especially when mental illnesses, specifically anxiety disorders are involved. I understand it must be frustrating to have anxiety for no clear reason, but do not beat yourself up. Anxiety is not something you have chosen to have.

It is not your fault. The best you can do is to go to a therapist or counselor or trusted adult to get help that you deserve and allow you to continue living a nice life.

Unfortunately, anxiety never chooses a mutually agreeable time to strike. Anxiety hits heavy and hard at seemingly any time, Anxiety disrupts your life when it is at its best, but also when it is at its worst or idling somewhere between the two. Regardless, you ought to focus on doing your best. Do not let anxiety trip you up. Take the anxiety in stride, keep your head up, and continue doing what you're doing that has allowed you to, as you say, "do so good in life."

Anxiety can be triggered at any moment. Finding small exercises or little reminders to calm you down can be a big help.

Anxiety unfortunately doesn't wait to hit someone when it is most convenient for them. It happens whether or not you are experiencing the better moments of your life. There are ways to reduce the anxiety though so that you can gradually get back to the way things used to be (or at least work with your anxiety overtime). Have you considered seeing a therapist? Practicing exposure therapy (either by yourself or especially with the help of a professional) can really help you to recover. I suggest looking exposure therapy up. I hope that this helps and I wish you the best of luck. :) As someone who has anxiety herself, I can assure you that you will be fine.

Anxiety can come and go depending on circumstances, but also it can come on randomly, which is both disappointing and confusing

This is a very good question, and one that a lot of people have. Anxiety comes when we least expect it, which is one of the things that make it so crippling, as you've said. Anxiety can come around when you're happy, sad, excited, any emotion. In the 'My Path' section of 7 cups, there is actually a really great exercise that talks about anxiety, and the on-off struggle switch that I would suggest that you listen to! It has really helped me, personally.