Grit

I've always said I was bloody-minded. Lots of people take that to mean blood-thirsty, which is incorrect. No, it's more of a stubbornness, a willingness to do whatever it takes to accomplish my personal goals. It's not ruthlessness, because that would imply that I'm willing to or even eager to hurt other people, but that's not correct. This doesn't have anything to do with other people.

No, it's the willingness to be ruthless with myself. To ignore my hurts and pains to keep going. Grit might be a better word. Particularly since the dictionary definition of "bloody-minded" seems to be "difficult to deal with : not willing to help others do things." The British define it as someone who is "stubbornly contrary or obstructive." Which are not the meanings I choose.

Yes, sometimes I made words mean what I want. Don't you?

“When I use a word,’ Humpty Dumpty said in rather a scornful tone, ‘it means just what I choose it to mean — neither more nor less.’

’The question is,’ said Alice, ‘whether you can make words mean so many different things.’

’The question is,’ said Humpty Dumpty, ‘which is to be master — that’s all.” 
― Lewis Carroll, Through the Looking Glass

But I think I'm going to use grit now instead of bloody-mindedness, if you don't mind and even if you.

It's just a question of who is going to be the master. I think.