Its hard to put into written word, but I also found that sometimes just permitting myself to be sad, and not fighting the feeling, did help it to ease in how sad I felt. For example, if I had a day I felt particularly down, I would notice/acknowledge it then do something which provided more TLC - sometimes this would mean I'd snuggle on the sofa, with something nice to snack on and watch a couple of films. Seemed doing this now and again gave me a rest I needed and I often felt a bit stronger to face the next day or challenge.
If a friend was struggling, we'd do similar things for them, sometimes we need to give ourselves permission to focus on ourselves. We are just as important and is not self indulgent atall.
If you find your mood is remaining at the same very low level, try introducing a little walk, or engage with nature a bit - I started feeding the birds and that became part of my morning routine, its a lovely way to start the day throwing food out for them and have them fly down - watching them, hearing the flap of their wings etc
Think baby steps - its a rollercoaster journey. Sometimes we expect too much from ourselves, sometimes we need to slow down or rest a bit. It helps if you look for little achievements each day,maybe write it in a little notepad. We used to do it here on the site, 3 positive things each day. An item could even be just a tasty cup of coffee, doesnt have to be big things, just whatever feels like an achievement. It helps our minds to notice the positive things xx