Edit: sorry for the long comment, but my username is partially a result (the metta part) for going through a period of having low self-esteem.

Tal-Ben Shahar Positive Psychology [1], it's a Harvard course and self-esteem is one of the lectures. It's old, but the big ideas that changed my life are there.

So based on that course you'll want to learn about meditation. I've got the right book for you from a Google engineer who made sure most of it was evidence-based [2].

Obviously you'll also realize because of the course you want to pickup aerobic exercise.

David Burns is my favorite psychologist (I read Intimate Connections from him, his claim to fame is Feeling Good). He has an answer to your question, which is Ten Days to Self Esteem [3]. Though, when I read the reviews you might just want to get one of his other books. I'm a fan of Intimate Connections, other people are fan of Feeling Good. You'll definitely learn a lot about cognitive behavioral therapy. CBT changed my life.

And what the heck, not sure if this counts towards your question, but it's at least related to it and good for the soul. Man's Search for Meaning by Viktor Frankl [4]. What's interesting about his book regarding self-esteem is that he basically invents half the field of positive psychology 50 to 60 years before it even exists. Also, it's just mandatory reading for any human being IMO, but that's again IMO.

Then, some personal advice that I've seen to work.

You need to be brutally rational and empirical about self-esteem. I know one programmer friend and I noticed that he wasn't able to do that. What I noticed was the following: HE DIDN'T TEST HIS ASSUMPTIONS! Yes, that warrants a caps because I told this to him every single time and it didn't get through to him. So, do find your assumptions and do some experiments.

Some experiments I have done in the past:

1. People are mean. Experiment: walk up to 10 people and say hi and see what happens. Result: people say hi back, and the pressure of not saying anything sometimes caused a conversation to happen which was fairly pleasant. In other cases it was awkward. In conclusion: people were never mean.

2. Stating to a woman that you want to kiss her doesn't work. Instead you have to make the move. Experiment: when I feel I have a bond with a woman [a] and I want to kiss her, then state it politely and leave it at that, repeat every 2 hours (if you still feel that way and have been fully platonic otherwise). Results: to my surprise, every woman kissed me. Heck, some just kissed me out of curiosity despite feeling no attraction to me. Weirder still, one of those curious kisses was one of the best kisses we both had in our lives. Note: I didn't ask any random woman on the street to kiss me. If the constraints of [a] weren't satisfied, I'd feel too unsafe to kiss her, and in almost all cases wouldn't even want to kiss her.

[a] Minimally 3 hours of intense talking about life, ourselves, our families, hopes, ambitions, the works, preferably 6 hours. This excludes having fun. Without getting a feel about someone and without feeling a strong connection, kissing feels a bit too dangerous for me to do. Since I had low self-esteem I wanted to feel safe.

3. I am not attractive. Experiment: go up to 30 people for which you want to be attractive to and give them a survey. Ask them at least: from a scale of 1 to 10 how attractive you are, and from a scale of 1 to 10 how attractive you could potentially be and what you'd need to change and why it would make you more attractive. While I didn't do this experiment, I have had enough feedback about my attractiveness. Long story short: I think I'm not that good looking (I have a scar on my face since birth). But most people that I want to be attractive to find me actually quite attractive. I've also been called ugly enough times, so ¯\_(ツ)_/¯. I think a strong moderating variable is whether you simply click with the other person in that moment.

What I've learned by experimenting: my assumptions and ideas about social interactions and dynamics are terrible. Sometimes I was right, most of the time I was quite to horribly wrong.

Other advice I want to give:

(1)

Self-esteem / confidence is knowing about understanding what you are afraid of and then understanding what success looks like, a successful failure case looks like and a horrifying failure case looks like. When I learned to ski this was crystal clear.

Successful case: I am able to turn, break and go straight.

Successful failure case: I am about to ski of a cliff, but I am capable of falling right now to break. I know that by falling it won't really hurt that much and I won't injure myself.

Horrifying failure case: (I had this one as a kid) you ski towards the ski lift and while at full speed you realize that you're going to slam into the ski lift row and you can't break (and can't realize that falling was a good option). Helloooo hospital, how are you? :D

Pick the topic and map out these 3 cases and try to find ways to make horrifying failure cases into successful failure cases. In the skiing example: if I just fell down before slamming into the ski lift row, I would not have gone to the hospital. Back then I didn't know that falling was relatively painless.

(2)

My self-esteem issue had to do with romantic relationships. What I learned was that if I was capable of giving me self love and didn't need a relationship, but see a relationship as the cherry on top, then life is awesome! And it was. One attitude that really helped with that was: treating life as playful and as positively as possible. I got all my relationships where I realized that I'd like one, but I didn't need one and I didn't crave for it. I learned how to kill the craving (thanks meditation).

So yea, hope this helps.

[1] I found a link: https://www.youtube.com/watch?v=K8qpn6kNfPc&list=PLF6A3AC0B7...

[2] https://www.goodreads.com/book/show/12921211-search-inside-y...

[3] https://www.goodreads.com/book/show/19295.Ten_Days_to_Self_E...

[4] https://www.goodreads.com/book/show/4069.Man_s_Search_for_Me...