I suggest trying meditating. Either once a day, or several times throughout the day. So for example, in the morning/before you go to work, maybe during a break while at work, and then after work or at night before bed. I prefer meditating before bed, along with other things like stretching/massaging to relax.
I would think that anything that relaxes you will also lower anxiety some too and will help your brain function better. Stretching, massaging, meditating, exercising, writing/journaling (using a pen/pencil and paper is more helpful than typing for some reason), etc.
I don't know how your brain works and what goes on in your head. But if there are certain things/thoughts that are distracting you on a daily basis, obviously one of the best things to do is work on those. If there is something bothering you about a relationship with someone, work on getting the courage to talk to them about it/think about what to say. If there are thoughts about yourself (appearance, behavior, etc) that distract or bother you, and you recognize that there are illogical/wrong, work on challenging them, replacing them with realistic thoughts. As you feel less anxiety, stress, and or depression from them and they begin to go away, you won't have to think thoughts about these things daily.
You could also always try using sites/games like Lumosity daily.
