Like you, I started ttc in my 30s. Sure, I waited longer than nearly ALL of my friends, but I thought 35/36 was still pretty reasonable... Unfortunately, it just wasn't meant to be.
I think what made it easier for me was my eventual diagnosis of POF (premature ovarian failure). With FSH levels above 150 and undetectable AMH levels, it was pretty clear that I would never have a child using my own eggs, so there was simply no point in continuing to try. As weird as it sounds, sometimes I almost feel lucky to have a crappy diagnosis like this. At least I didn't have to go through cycle after cycle of OE IVF or try any other ART procedure - it was either DE or adoption. Period.
Regardless, I felt like you do for a very long time and I still have times where I feel that way. There are days when I'm completely overwhelmed by the unfairness of it all - I mean, how is it fair that I'm paying 10s of thousands of dollars and going through emotional hell to try and have ONE baby, when so many of my friends have 3 or 4 without even thinking about it? The bottom line is that it's NOT FAIR. It's just not. But we can't change it, and maybe that's part of what's so frustrating.
I wish I could tell you how to get over it. I agree with the other posters that it probably takes having a DE baby to truly do it, but since I'm not there yet, I can't say for sure.. I just know that at some point I had to accept that it was either this way or no way, and most of the time I'm ok with that. Or, maybe I should say that most of the time I've come to accept it. Here's the positive side - at least we can do something. 30 years ago, this wouldn't have been an option, but at least we have technology on our side and this can and does work for a lot of people. I know it's hard, but focus on that, if you can.
Sorry for rambling, but I hope something I've said resonates with you.