I quit my super stressful job which was giving me huge anxiety and depression. I was also having what was almost like PTSD a year after my husband recovered from cancer, when he was sick things were also very stressful and I was sort of reliving those feelings. Took a year and did my own thing, tried different hobbies and jobs and eventually found my current job which is much less stressful. I was a huge mess 3 years ago, I could barely leave the house. I did cognitive behavior therapy to get over my anxieties as well as a lot of soul searching to find a job I'm passionate about. I wasn't actively trying to improve my thyroid levels though I guess it was just a side benefit of becoming well.
From my research TSH does fluctuate day to day and even from morning to night though I think it's rare for it to fluctuate more than 2 points in a short time. Under 5 is in the current "normal" range but a lot of endocrinologists are saying the number should really be a lot lower because people with a TSH above 3 are usually not at "optimal" levels and may benefit from treatment. Most OBGYNs and FS like TSH to be below 2 especially for TTC and during the first trimester because that is when you are sharing thyroid hormones with baby, after first tri baby's thyroid starts working on it's own.