As a therapist, I offer many different skills depending on anxiety symptoms. I don't know if I can say I have a favorite skill...but if I did, it would be this one: Leaves on a stream (only takes 3 minutes and 33 seconds). It is an efficient tool to help reframe your thoughts and increase calm and employs what is called cognitive defusion.
"Defusion is really about changing our relationship to our thoughts by observing them rather than engaging them. According to Acceptance and Commitment Therapy, it’s not the thoughts that are the problem; it’s what you do with them." ( https://cogbtherapy.com/cbt-blog/cognitive-defusion-techniques-and-exercises)
Think about it, we have all sorts of thoughts all day long. There are some we dismiss as we feel they are irrelevant and some we hyper focus on and feel they have to mean something. These thoughts can be so automatic that we are not even aware of them. In other words, there are some things going on contributing to anxiety that can be resolved, typically in therapy. Cognitive Defusion is an important concept as anxiety isn't entirely based off of a situation but our reaction to the situation. So, if you have 3 minutes and 33 seconds, it's worth a try. As with many skills, it is a practice and not a destination. If you're having the thought of "I'm not doing it right" or "this isn't working," place it on a leaf (as mentioned in the exercise).