Anxiety is caused by a form of ruminating about the future in which you focus on uncertainty. Get out there and eliminate all uncertainty and you will feel your anxiety disappear! Tell your boss you feel unappreciated, talk to strangers, and generally do things that you feel anxious about.
If your anxiety is so strong that you can't do those things, then get therapy! It changed my life, and a good therapist can change yours as well.
I think it's great that you are sharing your personal experience. This can help others. But saying "and a good therapist can change yours as well" is a dangerous thing. It worked for you but you can't know for sure if it will work for others.
Share your experience but don't tell others that your way will work for everyone.
I don't see any connection between what I wrote and your reply.
In any case, you are wrong about the cause of anxiety. That might be a cause of it, but there are plenty of other causes. See in particular the "medical causes" section of http://www.mayoclinic.org/diseases-conditions/anxiety/sympto...
It can be a symptom of an underlying illness.
The OP seemed to indicate a mild social anxiety to share their ideas, not a crippling, clinical anxiety that requires professional attention, so "stop being anxious" is a perfectly valid piece of advice. IMO the easiest way to get over imposter syndrome is to "fake it till you make it," which is another way of saying "stop being anxious and do it anyway."
This implies that anxieties themselves have no causes.
> Stop being anxious
I'd like to see your advice on other things. "Stop being sick!", "Stop being afraid of spiders!", "Stop being introverted!"