Rumination, or obsessive over-thinking about one’s situations or life events, is linked to several different kinds of psychological distress. It is probably the symptom most commonly spoken of by people suffering from depression and/or anxiety, and it plays a key role in sleeplessness, eating disorders and a list of other complaints.
As a coping style, rumination is more hindrance than help, but does that make it a bad habit? Not entirely. Like anything we can do with our thinking, it has its uses, but equally, just as any other aspect of thought, it can be a nuisance if it becomes generalised. Over-analysis can leads to paralysis.
The ability to look at things in detail, from many different angles and theorise about potential solutions can be very useful as far as it goes, and when it leads to meaningful action.
But problems arise when someone loses the ability (or has never developed it), to turn the thinking into action or, if no action is appropriate, to simply say “Let it go”.
When you can do that, you’ll also be able to say “And the fears that once controlled me, can’t get to me at all”, just like it says in the song.