I was taught some CBT techniques for the anxiety.
First just focus on breathing in and out three times, slowly.
Then I practise asking myself:
How is this anxiety improving the situation a) for me b) for anyone else? (Answer, they aren't)
Am I forecasting (anxious about stuff that hasn;t yet happened so may never happen) or mindreading (anxious about what other people might be thinking when I have no way of telling what they are really thinking) If so, how are these helping? (Answer - they aren't.)
Then I talk to myself in my head with quite a firm but kind voice and say: OK, we're stopping this right now before it grows bigger and out of control.
Then I use a distraction technique: So instead of fretting I will now [add something very easy but distracting that you can do immediately, even if it is just reaidng the posters on the tube stops, or making a shopping list.]
Then I congratulate myself for having lowered the anxiety - That helps, well done for doing it, Keep doing it.
That set of techniques does help as there is something i was getting obsessively anxious about and I have managed to lower the anxiety to manageable levels.