Not everything that is going on in your mind is of equal importance. It is necessary for you to figure out what matters the most. Certain things might be bothering you because they are actually of relevance while others can be sometimes just figments of your imagination.
Separate out what matters the most.
Let go of the rest.
Anything that you deem to be not as important you must let go. It can be a very difficult feat to achieve, especially if you are anxiety-prone. But, with practice, you will find it easier to manage.
Even the toughest things become doable with practice. If you can persevere and stick to it then it will become a habit.