Anxiety UK suggests practicing the 'Apple' technique to deal with anxiety and worries:
Acknowledge: notice and acknowledge the uncertainty as it comes to mind.
Pause: don't react as you normally do. Don't react at all. Pause and breathe.
Pull back: tell yourself it is just the worry talking, and this apparent need for certainty is not helpful and not necessary. It is only a thought or feeling. Don't believe everything you think. Thoughts are not facts.
Let go of the thought or feeling. It will pass. You don't have to respond to this. You might imagine this thought floating away in a bubble or cloud.
Explore the present moment because right now, in this moment, all is well. Notice your breathing and the sensations of your breathing. Notice the ground beneath you. Look around and notice what you see, what you hear, what you can touch and what you need to do. Reflect on what you were doing before you noticed the worry or do something else - mindfully with your full attention.