Swallow your pride, always be questioning what you are doing and how you can do better, and never give up.
It can be discouraging to read sites like HN where everyone and their dog seems to have 18 different offers from Google/Facebook/etc with recruiters begging at their feet. This is far from the norm.
I went through a similar phase before my current employer - I had only ever worked for agencies/tiny family run companies/etc, and I wanted to work for a real, “legit” company. This resulted into rejection upon rejection, even when I thought I had nailed the interview. I remember one that hurt pretty hard - I got scouted by Airbnb because I had given a talk at a fairly large, reputable conference, and their VP Eng at the time reached out to me. On top of that, I got recommended by a friend who used to work there and whom I believe to be one of the very best engineers I have ever met. I know he wouldn’t have recommended me if he didn’t sincerely believe I would have been a good fit. Halfway through the day of on site interviews, the recruiter comes in the room and tells me that they’re not going to move forward, and that I can go home. (my friend met me downstairs for a cigarette right after, and while I do not regularly smoke this was one of the best cigarettes I ever had).
Lowering your standards and interviewing for companies that don’t seem that interesting is probably a good idea too - extra practice, and even if you get an offer that you don’t accept, it’ll make you feel a bit better.
I will say that not having a top institution (either college or employer) on your resume definitely gives you a huge handicap, especially in the Bay Area. All my schools/employers at the time were names no one had ever heard of, and it definitely felt like I was in a different world compared to friends who had gone to Stanford/MIT/Google/etc.
In the end, I found a position with a team that was ideal for me, but yeah - it took a lot of sweat, effort, and perseverance.
Your age probably does not work in favor (sorry about that). Keep interviewing, and do publicly viewable things (open source contributions, blog posts, conference talks, etc) - these will not only help you stand out, but will also help you feel good about achieving something, because one certainly does not get that from interviewing.
Good luck.