The closest definition anyone can give for anxiety is a troubled relationship with certainty. The more obsessively we think that we have to know, the more anxious we become. Look at the pattern:
Everything we do to excess comes from fear. And what do most of us fear? Uncertainty. So we think that if we do more, we'll be able to engineer the outside world, and we do everything we can to make sure that everything is fine. Whether that's making sure everyone likes me and nobody rejects me, or obsessive planning so that, heaven forbid, nothing takes us by surprise. The catch is that the harder you try and the more you do, the less calm you feel. Just the opposite! You raise the anxiety! Which means that the chase after certainty is what ends up causing our anxiety.
Our inability to tolerate uncertainty makes us try to take control back through overthinking and overdoing, attempts to create a feeling of certainty that of course never arrives. What they actually do is signal to the brain: there's danger, stay alert, we aren't safe. The only cure for anxiety is to do the thing you're anxious about. Not once, not twice, not three times, but again and again, until you trust yourself more than you fear the unknown. Anxiety leads to avoidance, and avoidance makes the anxiety bigger. It's a loop, and it runs on the equation that comfort equals safety, meaning that the system reads discomfort as danger, which of course isn't true. Talking to your mind won't help. It doesn't understand words, it understands behavior, and so the goal is to feel the fear and act anyway! Again and again! Until your brain catches up with your courage!
Not one of us experiences objective reality. We experience reality through our nervous system. Reality I can't change. My nervous system I can.
The goal is for your nervous system to be able to carry the discomfort, to get your nervous system used to feeling safe in the unknown. Success isn't having certainty and then feeling fine. Success is knowing that even in the situations where I have no idea what's going to happen, I'm going to be okay.
Get this into that beautiful head of yours: it's exactly when nothing is certain that everything is also possible. For the good!