Start with what low mood does, mechanically. It drains energy and shrinks appetite for everything — people, projects, even things you used to enjoy. So you do less. That's not weakness. It's what low mood is *for*; it's the body pulling inward.
But here's what doing less quietly removes from your days:
Take those out, and mood drops further. Which drains more energy. Which shrinks life further. Around it goes: low mood → less activity → fewer rewards → lower mood. That's the downward spiral. Not a character flaw. A loop.
The critic in your head has a different theory. It says the doing-less is evidence — proof of something wrong with you. "Lazy" is usually its word. But look at the mechanics: everything you've been doing, or not doing, is exactly what this loop produces in anyone caught in it. The spiral is the explanation. You are not.
And loops have a useful property: they run in both directions. The same mechanics that pull mood down when activity shrinks will lift it when activity — carefully, gradually — comes back. That's the entire program, and we'll walk it one small step at a time.
Where you are on the spiral matters less than which way you're moving. Someone at a five and sinking is worse off than someone at a three and climbing. Direction beats position. Your evening check-ins are already measuring both — that's why they matter more than they feel like they do.