Spaciousness of mind is always available to us. We just need to access it. - Andy Puddicombe.
Because thinking is a process we usually take part in unconsciously, it's no surprise that many of us forget that we can change the way we think. Rather than simply accepting the thoughts that cause you so much anxiety, you should challenge them.
Step One: Identify your thinking errors. If you don't know what a thinking error is, start by reading about them here.
Step Two: Ask yourself if there's a better way to view your situation. Hint...there is.
Step Three: Create a more empowering alternative story to ruminate on.
Step Four: Repeat the above steps.
Habits take time to build and time to break. Because you may have been making so many unconscious thinking errors without realising, give yourself some grace as your work on improving them. Talk about the challenges you're facing with someone you trust.