I like the sound of this, but I'd have to adopt the mindset of "I am such a great person, I enjoy my own company, even though others don't enjoy my company." "That girl that just ignored me missed out on a great guy."
If I was a man that had had relationships, and had a woman/women express interest in me and enjoy being with me, I'd find that so much easier. I'd be able to refer to those experiences with women in my mind, and know that any woman that rejects me missed out on somebody that has showed other women a great time.
I can keep telling myself that I am a great guy, that they missed out. That I enjoy my own company all of the time, and that I am developing myself. But they really haven't missed out on anything. They meet a funny, smart guy that is relatively, or really good looking, and then they're happy. I am still that non-entity that they take no interest in because I walk funny, appear meek or timid, or am just plain ugly. Or all three.
They have not missed out on anything.
I feel that to develop myself in the manner you describe, I'd need to have or have had healthy relationships. I'd need to have those emotional connections.
The first step is to stop making excuses. You know what you're telling me in some manner can be seen as an excuse, which to you is qualified more as a rationalization.
Just do it. Don't think about what other people think, don't think about why you need to do something that benefits you, don't think about why you didn't do it today or skipped out on it. Just do it.
Getting some sun, exercising, trading some of your wasteful personal time into productive personal time, is not demanding except for the fact that it isn't your current habit and honestly, that is really the source of that negativity. A resistance to change and effort.
We invest in things all the time but rarely do we often work ourselves as we do our videogame characters, but we innately know that the more time we spend on them, the better and more experienced they become.
You are the person you define yourself to be and you won't have to think a certain way if you already are a certain way. This is not a race and you quite literally have decades of life in front of you. Fill it with things and stories and frankly, everything else pretty much takes care of itself including women and relationships.