https://www.healthline.com/health/mental-health/how-to-survive-midlife-blues
Depending on how old you are, you might just be hitting the normal midlife low point. It hit me hard in my late 30s and I spent a lot of time reading about it once I found out it was typical. I think a lot of it has to do with the rate at which you’re experiencing milestones and life changes. It feels like you are constantly progressing in your life up to your 20s or 30s and then the time scale suddenly shifts. Things take much longer to advance - saving enough for a house or retirement, that next promotion (assuming you even want one), major family changes, etc.
Understanding that helped me recover somewhat, though it still took a couple of years. I’m still in that lull, trying to figure out what I really even want to do next, but I don’t feel sad about it anymore. I don’t know if this applies to your situation, but I found it really helpful to learn about it.
I use a budget app for tracking income and spending on a transaction basis and then keep the rest of my finances in spreadsheets.