Throughout history, until barely more than a century ago, fabrics were costly and clothes were handmade, so we preserved them for years, or for generations. Like these remarkable early-eighteenth century farm laborer's trousers.
My book MEND! A Refashioning Manual and Manifesto is about the whole darn mending (and vintage) thing, from the history, to the reasons, to the practice, with copious instructions and mendspiration.
I started visibly mending many years ago, and I've been sewing all my life. My mother taught me, as her mother taught her, and so on down the generations. But despite learning how to sew properly, I've always preferred making it up as I go--and that's what VM is all about. There is no wrong way. If it works, it's correct.