ok. I completed Angela's method on "I'm useless". After writing five pages of stuff down, it became obvious that it all boiled down to... Freedom.
I realized that without this belief ruling my life, I wouldn't feel the need to prove that I'm not useless. So I wouldn't feel pressured by myself into contributing and helping others and doing only useful things. I'd be free to do so, or not. I'd be free to contribute out of love and joy, not out of duty. I'd be free from guilt, free from this emotional debt!
I also wouldn't be forced to confirm "I'm useless" over and over again. I'd be free to contribute (because that's really what my heart wants), and also to finish the things I begin with. As long as I believe that I'm useless, I cannot make a meaningful contribution consciously, nor can I finish my projects (cuz they would be a valuable contribution, thus I wouldn't be useless anymore). As long as I believe that I'm useless, I also have no chance whatsoever to discover my purpose (cuz if I have a purpose, as in a function, I'm by definition not useless), and I have no chance to fulfill my purpose either (this would be useful for the highest good of all).
In fact I discovered that believing "I'm useless" and simultaneously obsessing over my purpose was pretty funny of me! Hahaha!
In some other post above I wrote something like "I think I'm useless, and that all doors are closed". I found it strange to talk about closed doors, but now I understand it. Believing that I'm useless didn't allow me to do anything useful and at the same time forced me to do only useful things. Urghs, failure garanteed!
Letting go of "I'm useless" allows me to do useful things without having to. This way I'm free to find my purpose, to fulfill it, to contribute, to realize my projects to the end... and at the same time I have no pressure anymore about having to do so, it's not a duty anymore. Isn't that freedom?

All doors are open!
ok, so here's the active part of the process:
I hereby commit to breathe out and peacefully let go of "I'm useless" every time I catch myself thinking it. If you all reading this catch me unconsciously being "I'm useless" in some way, please let me know!
I commit to generating Freedom and Harmony for myself, you and everybody else at every moment of my life
Thank you and Amen