In roughly this order
You do not have to do all of it. Doing the first two is worth more than reading all of it.
1
Start with sleep, because it multiplies everything else
Poor sleep raises the stress response and blunts judgement, and it is hard to do careful work — including careful applications — from inside that. Rejection then does its own damage to sleep. Whether the loop runs exactly that way for you matters less than the fact that sleep is usually the most tractable place to interrupt it.
2
Then the body, because the fog is often physiological
Feeling less capable than you know yourself to be is frequently a stress-response state rather than a change in capability. Movement is the most accessible intervention, and if you are over 45 there are physical causes — hormonal, nutritional — that produce symptoms easily mistaken for low mood, and that are sometimes missed for a long time.
3
Then money, because financial fear masquerades as everything else
Vague financial dread expands to fill whatever space it is given and shows up as irritability, insomnia and an inability to concentrate. Converting it into specific, dated numbers often makes it more manageable, even when the numbers are bad.
4
Then people, because withdrawal is quiet and fast
The reluctance to socialise — because socialising means being asked what you are doing — is very common and makes everything else worse. Having a short honest answer ready removes most of the obstacle.
5
If it has been more than two weeks, this is a GP conversation
Persistent low mood with real impairment to daily function, difficulty getting out of bed most days, withdrawal from people — these are clinical signals, not evidence of weak coping. You do not need to be at your worst to ask, and earlier is a shorter road back.
The three topic pages most worth your time from here
If you would rather not choose at all, the anxiety page and the sleep page are the two that most often help first, and both have something you can do in the next ten minutes.