I was diagnosed with OSA in 2017.
Because I live on my own no-one had ever noticed my snoring, but when I stayed over at my parents one Xmas my Mum noticed my excessive snoring.
I was always falling asleep in meetings at work and often got pulled up on it.
So given this I went for tests... severe OSA and given a CPAP mask! I was shocked - I knew some friends with this and they were all morbidly obese. I was fairly fit and overweight (49 at the time), I am male (just for info) and back then I was drinking which doesn't help (stopped now). They told me I had a narrow jaw and airway which caused the OSA.
So I started with the CPAP and it was odd at first but it IMMEDIATELY cured the OSA. No more falling asleep at work, feeling fresh in the morning, no tiredness during the day - it was like magic!
So I would say CPAP can indeed change your life - but you have to stick with it, and experiment with different masks. Your attitude to it helps - I was horrified at first, but soon came to refer to it as my 'Sleep Machine' (my latest one is branded DreamStation!). Once it's on, that's it, I'm off to the land of Nod all night (except for the odd nocturnal wee - one of the joys of being a middle aged bloke).