If you have tried the typical advice of keeping a positive attitude, sleeping more, or exercising and found these have had no real impact, it's not your fault.
They work well in people who don't have chronic anxiety but instead have a test coming up, an important presentation, a big event. If you have experienced anxiety for a long time or have had a significant emotional experience cause your anxiety, you need different tools.
Understand that your brain has adapted to the experiences in your past. As a result, you are not only more sensitive to stressful experiences, but when something does happen, your body releases a much more considerable amount of stress than the average person.
It's nothing you have done, and it is tough to get a handle on when it does happen. But, by having clarity about what needs to be improved, you're in a much better positive to do so.
If you know someone living with anxiety (and pretty much all mood disorders), understand that everyone's body automatically reacts in a certain way when confronted with stressful events. An experience that triggers a stress level 2 for you may trigger something comparable to a stress level 8 in them. Neither of you consciously chose the response. It happened automatically. But they're now having to deal with a body that is in a state of panic.