Why 'don't compare yourself' is a rubbish piece of advice

Oh well, here we go again. I'm saying the opposite to the rest of the internet, what a surprise. 

I suppose I am having a bit of a moan, but what I really want is for this to be super helpful and hopeful. 

We are told constantly not to compare ourselves. We are told by our best friends and our parents and by motivational writers and quotes on the internet, mainly. I feel as though all of these people are either forgetting, or choosing to ignore something fairly important. 

I absolutely believe that people aren't worth any less compared to any other people. I love the quote 'no one else is you, and that is your power' - nobody else has all of your attributes in your quantities and that's what makes you so unique, and that's the most wonderful thing.  

I also wholeheartedly believe that Comparison is the Thief of Joy. If you spend your life comparing yourself to other people - whether that be your appearance, your grades, your possessions, or actually anything - for no reason - you will be miserable. The key thing there though, is the 'for no reason'. Are you achieving anything? Are you actively trying to change it? Are you using people as your motivation or are you using them to make you feel less worthy and inferior? 

Comparison is literally how life works. 

If there's a reason though, there's a place for it. There's a place for healthy competition and for having goals in life - which is always going to involve comparison. 

Want to go to university? Want to get an internship? Want to be picked up by a brand to collaborate with online? Want a part time job in retail on minimum wage? Want to make the shortlist for an award? Want to gain a part in a play? Want an Oscar? Well, I hate to break it to you, but you're going to be compared to every single other person that wants the same thing. And there won't be a shortage of them.

I'm not really sure how we're supposed to deal with that. I'm not sure how we're supposed to deal with the fact that the whole world is telling us not to compare ourselves while actively comparing us to other people.

Any ideas?