When I reflect on my own career, I see some failures rather fortuitously avoided.
As a child, I wanted to become a theoretical physicist. I went to Warwick University in 1969 determined to study the subject. For various reasons that all went wrong, but today I read at Backreaction Sabine Hossenfelder's experience:
"I finished high school in 1995. It was the year the top quark was discovered, a prediction dating back to 1973. As I read the articles in the news, I was fascinated by the mathematics that allowed physicists to reconstruct the structure of elementary matter. It wouldn’t have been difficult to predict in 1995 that I’d go on to make a PhD in theoretical high energy physics.---
"Little did I realize that for more than 20 years the so provisional looking standard model would remain undefeated world-champion of accuracy, irritatingly successful in its arbitrariness and yet impossible to surpass.
"We added neutrino masses in the late 1990s, but this idea dates back to the 1950s. The prediction of the Higgs, discovered 2012, originated in the early 1960s. And while the poor standard model has been discounted as “ugly” by everyone from Stephen Hawking to Michio Kaku to Paul Davies, it’s still the best we can do.
"During my professional career, all I have seen is failure. A failure of particle physicists to uncover a more powerful mathematical framework to improve upon the theories we already have. ... "
In my early twenties I was a reasonably-successful member of the International Marxist Group - I was on the National Committee. Just a few years later, I became disillusioned - just a gut feeling that something was wrong with Trotskyism and that the revolution was not going to happen. Most of my comrades of the time remained in left politics their entire lives.
I mention John Ross, the IMG leader and latterly Ken Livingstone aide on the GLC, and Kate Hoey, now a Labour MP, amongst many others.
Still, the revolution never happened, nor are we any nearer to it.
In my thirties, at Standard Telecommunications Laboratories (STL) in Harlow, Essex, I worked on my PhD in artificial intelligence. By 1990 that funded research had terminated with the takeover by Canadian telecoms giant Northern Telecom (Nortel).
I briefly considered a career in academia as an AI researcher but there was no obvious possibility, so I bit the bullet and retrained as a telecoms network architect. It proved both interesting and lucrative over the next 25 years.
Had I stayed with AI, I would have entered the twilight of the classical AI research programme known as GOFAI. The field became moribund until the recent explosion of 'deep learning' in the quite-variant neural net tradition.
So looking back, I had an opportunity to dedicate my life to changing the world in a political tradition which has proven ineffectual plus two opportunities to push the boundaries of knowledge forward .. in areas where history shows that nothing of great worth emerged.
Instead I got to design a lot of state-of-the-art networks, some of which even got built.
Engineering may be less ethically-challenged than many other professions - but I'd still rather have done the science.