Here is why — there’s a saying from a bigger text that reads like this:
“When you compare yourself to others, you may become vain or bitter.”
And I think that’s definitely a danger.
Also, when you spend a lot of time worrying what other people are doing, you take away your own personal focus from what you’re doing.
In some cases, that will make you mentally ill.
Being overly obsessed with something, especially when it’s not going well, can have a negative impact on your mental health.
Focus your energy on your current task, not what someone else is doing.