I don't see her happy with me because I'm just so worthless. I can't give her anything.
I feel as though I do have to say goodbye. No point in her wasting herself on a loser like me. She deserves someone who can actually DO something for her. And I love her as well, so I want to do what will ultimately make her happy.
Don't be dumb. How many chances do you think you will get in a lifetime like this? Are you going to let both of you be miserable or you are going to try and Make yourself into someone worthwhile? She wouldn't be in love with you if she doesn't see some merit and potential in you.
See, we are not born as extraordinary babies, we make ourselves competent and unique and whatnot. A large part of growing and becoming more mature and capable has to do with trying new experiences and taking a chance.
She has faith in you and you can either let her down or step up. I know this is hard, I struggle with this too. But to face tough situations is what makes us ultimately "worthwhile". If you two don't work out in the end, you will have gained valuable knowledge and experience. You would have known you gave this a chance and tried your best.
Maybe you rather harbor it as some sort of secret, idealistic dream and find comfort in it. I agree that you should talk to her, lay it out there, listen to what she has to say, clearly state your areas of concern...
No pain, no gain, no risk, no reward. It's not like you are worried about ruining your best-friendship anyway since you are just going to let it go.
This is something I would say to myself.
Recently, I gave a guy a chance and myself a chance. It didn't work out and when it didn't, it was like being hit with a book full of my weaknesses and worthlessness. But I got over it in uhm two days because I told myself that I could either make myself feel bad or I accept it without the past garbage and appreciate myself for not letting this be some sort of weird, idealistic thing in the back of my mind and giving this a chance. How good I was at it is debatable, but I did my best... and now I don't 'wonder' about it anymore.