Jack of all trades, master of none

This is actually an incomplete idiom, cut off in a way that makes it sound more negative. The original was intended as a compliment:

A jack of all trades is a master of none, but oftentimes better than a master of one

I am the same and I fully embrace it!

Jumping from one thing to another is not good long term.

I don't see why. Ever had a conversation with a PhD scholar about anything other than their particular field they dedicated 30 years to? They are largely complete ignoramuses, for the most part, and exceptionally dull.

The point of pursuing interests is less about mastering the function of one subject, and more about how it rewires your brain. Maths in school for example, isn't really about mastering trigonometry. The biggest benefit is making you more analytical, more patient, problem solving.

Every different thing we dabble in builds our minds to be more versatile, balanced and healthy. We learn to be more social, rational, articulate, philosophical, humourous, content. Ultimately, these will be the things that matter, and you'd be surprised how they can blend in ways you wouldn't expect, career-wise

I think it was the luxury brand Hermes maybe? They started off making saddles for horses. They saw cars taking over, and moved to luxury leather, and the rest is history. Nobody would guess a horse saddle maker would become a high street fashion brand!