These were really such a source of dread for me. In high school and college I stocked up on Murad cream, vowing to religiously apply the product twice a day. I was determined to get rid of these pesky marks. Of course, the cream didn't work (but also I didn't love the smell of it so the routine didn't last too long).
When I had first googled them in eighth grade, I understood stretch marks to be irrefutable proof that I was fat -- and in my teenage brain that was shameful. When I went swimming at camp, my tummy used to be the area I had to hide, and now that shame had migrated to my thighs. There was just this overwhelming sense of 'I don't like my body as it is, and I cannot keep up with these curveballs'.
My stretch marks still aren't in my top 5, but they don't upset me anymore. Mainly because I've seen that pretty much everyone has them. And they don't look bad at all on other people! They're basically beauty marks with bad PR.