All my life until now I have devoted to studying and career and focusing on getting the top results and this is why I have not had the time for a relationship. I believed that this tactic worked well for me and was good but despite my outstanding achievements I now understand  I have missed on important stages of life . Recently, I started to feel depressed by feelings of jealousy when I see happy couples everywhere.

This is how the problem actually originated. 
Where I live there is this couple who are exactly ideal. They seem genuinely in love with each other. During the covid pandemic I stayed at home all the time and unwillingly became obsessed by them (as they are one of the few young people in my neighbourhood). They are around 3-4 years older than me . When they moved in I was hopeful I would be like them soon and felt good seeing them, but now that nothing has changed when I see them together I get depressed knowing that they are having fun and I am single. Knowing that they sleep together spooning each night, while I sleep on my own makes me frustrated. I want to stop thinking about them, but when I see them, which is impossible to not happen, I start feeling like that they are winning in life and I am losing. I am afraid that they will continue to be more and more happy - have children and raise them, have grandchildren and live their old days in happiness, while I die single. Also, they seem to be pretty rich, despite their young age, so that makes me more jealous. 


TL; DR: I feel depressed as I am loosing out on important stages of my life, I have no reason to belive it will get better and also feel jealous of others, because they have what I want.