One of reasons we suffer with anxiety is due to holding on to the feelings created from the past. When it comes to anxiety, our brains tend to retain the bad thoughts or the bad feelings and the good memories become foggy. The bad stuff starts to replay on a loop and anxiety feeds on this type of thought process.
The thought process then becomes a way of life and gradually it gets applied to every aspect of life. When we endure a negative experience we associate a "bad feeling" to it. So if a similar experience presents itself again, we assume it will play out the same way as before. This is when we tend to "predict the future". This leads to feelings of anxiousness, panic and avoidance. Then we miss new opportunities out of fear and this keeps the anxiety alive.
I wish I could tell you this was something that had a magical cure and there was a switch you can flip to turn it off. Sadly, there isn't. It takes time to amend this type of thinking.
It takes time and practice but the key is to recognise when your mind is thinking negative thoughts. These thoughts tend to be automatic, so this is why its tricky to recognise. Once you get used to this, you can alter the thought process.
When you hear the thought saying "I can't do this", challenge it. Why can't you do this? What's stopping you? What is holding you back? I am willing to bet fear from anxiety plays a part in the answer.
When you hear the thought saying "Last time I tried this, x happened", challenge it. How do you actually know the same thing will repeat? Are you suddenly able to see the future? There's only one way to find out how any given situation will play out; drop the clutter from the past and reach for the new opportunity.