I've read that the saying "Tsuyoku naritai" ("I want to become stronger") is used in the context of sports competitions, where it expresses the drive to improve (not necessary only in strength, but speed, skill, etc.).
A Japanese friend of mine said it's not appropriate in the context of aikido, because aikido isn't competitive. But I wonder, couldn't it still be used to describe the will to overcome your own weaknesses, to express the drive to constantly become better than yourself?
I'd be grateful if our wise and experienced Japanese speakers offered their insight. (And an actual rendering of the words in Japanese would be welcome, too, as I'm having a hard time Googling it, what with cross-linguistic difficulties and all.)