When I saw the title of this post I thought you were past retirement age!
I lived in Nuremberg from 1982 to 1985. I was 36 when I moved there for a job with the US Army. I had gone to Europe for 4 months 1977 to 1978, obviously pre-Schengen. I quickly learned that there was no way I could easily get a job there legally, so I went back to the US to work on that. It obviously took awhile to accomplish that goal.
You haven't said what career you want to get, but if you truly love travel as much as you say you do, perhaps you should consider alternatives in the travel or tourism industry. It would be a job and not necessarily a joy all the time, but perhaps one that would be truer to your nature than whatever "grown up" career you think you should have.
People back home thought my job in Germany somehow allowed me to travel all the time. I'd have to remind them that I worked 40 hours a week and had to do all the normal things they did at home. And that I was accruing vacation time just like in a job in the US. However, my schedule was such that I could create 5-day weekends to pop over to Paris or up to the Netherlands, or...
Some people thought I was a little crazy because they couldn't imagine that I would go to a job in Germany without knowing a single soul there.
But I was used to that. People thought I was nuts when I quit my job at the university in 1977 and sold almost everything I owned to generate enough money to make that 4-month trip. Most were so entrenched in their jobs, it was incomprehensible that I'd leave a secure job without going to a better job, much less take off on such an adventure.
I'm sure you realize that you have to jump through lots of hoops to get legal permission to live in Spain for longer than 90 days. And that the chances of getting a legal job there are slim and none, even if you are fluent in Spanish. I'm sure others more knowledgeable about those issues will chime in.
My advice is that in spite of the work you will have to do to accomplish this goal, don't give up on this dream.