Help! I hate my hair. Feeling defeated.

I have struggled with frizzy, unruly hair my whole life but I’ve been super frustrated with it lately. I got my first color job last year and had been so fed up with frizz and it looking like a rats nest (the back portion is the worst) I had been using a flat iron (on lower heat setting) a bit more regularly this year. I’m afraid now that’s just made it worse… how do people not have to style their hair every day and have it look nice ?! Even if I get it to behave, after sleeping on it once or working out (sweat) it reverts to this monstrosity. I wanted to get the highlights refreshed but I don’t even want to bother as I assume that will just agitate it more. I’m so frustrated with it. Any help or advice would be greatly appreciated..