Screamernail,
thanks for sharing your story.
It is important to know that a lot of people are going through what you are experiencing. Be it in their 20s or later in their 40s or 50s. You are not alone!
You said you only have unfinished projects and that you feel you are wasting your life on nothing. I don't think this is necessarily the case: Can I suggest you look at some of your work and instead of seeing only discontinued projects, you look out for the bigger picture, i.e. what did you learn doing these projects, how did you improve from one to another. Even if unfinished, there will be some sort of process noticeable! And this is already a good sign. It's a sign that you are not wasting your life, it's a sign that overall there is (even when unfinished) progress.
I had similar problems before I went to university to study design and architecture.
What uni taught me is to realistically assess:
a) My skills at this very moment,
b) Work out a realistic schedule for a project
c) Setting own, do-able deadlines and stick to them
And finally d) Do not get caught in details but rather scale back on the scope of work to actually get it done.
Basically It boils down to get to know yourself better:
a) What can you do?
b) In what time can you do it?
c) What do you want to achieve with this piece of work?
The last one is really important: Always have an idea (like a single one) behind of what you are doing. Every great map, every great game, movie or piece of architecture usually had a single good idea behind it, spanning over the entire piece of work. This makes it easy for you as a designer to keep the project and yourself in check. You can always double check if what you are doing right now is still working towards benefiting your idea. If it doesn't, take a break and think about what you are really trying to achieve.
The "one idea"-concept is a VERY powerful tool in design. It will also make sure that you do not waste time on minor details that don't matter in the end.
Example: Crossfire (Half-Life Deathmatch map)
Crossfire's idea was, essentially as the name suggests, to create a fast paced space where there is a lot of crossfire going on. The buildings with their windows and balconies in the main area are set up in a way to mimic close quarter combat. You can shoot (or being shot at) from all directions, there are some spaces for you to hide and regroup and there is the helipad outside with the one bunker to go in (by the way, IMO the map would work just as well without that area).
This is a cool map everyone loves to play. Why? Because the idea behind it is good! It's good for HLDM and its weapons. But is it a particularly beautiful and detailed map? No. The architecture is smart and effective but very simple. There is not a lot of complex brushwork going on, the map uses like a total of 10 textures or something, the windows don't even have frames or glass in them, there are no doors or sophisticated lighting effects and the elevator platforms couldn't be any more simple.
But still, someone had a good idea and built a map with the focus only on things that help to get the idea behind it across. And it rocks. You don't actually miss anything and it's done.
To wrap it up, my advice for you is to write down an idea you think you'd like to show off and then build something on top of it you KNOW you can pull off. Scrap everything that doesn't help to get your idea across and set a realistic deadline for your project. Don't worry if it is not perfect! It takes courage to "call it a day" and upload what you got. Better have a finished project that has some flaws than a few gigabytes of unfinished content nobody will ever see. This is how you will see a lot more progress and it'll become easier and easier for you to finish one project at a time!
You're a good person and you can do this!