When I was young, when people who were going through a difficult time were asked how they were they'd often say "Oh you know, keeping busy."
If I wa feeling a bit low my mum would find something to occupy my mind.
I even remember being told to do exactly that by a doctor when I was struggling with some bad news.
As an adult, if I'm struggling with life my coping strategy has always been to do something useful or plan a project to distract me.
I completely understand that for serious depression or other mental health issues other measures are needed but for "low mood" or the low feeling that we all have when things aren't going too well for us, is keeping busy no longer a recommended strategy?