Re: the true meaning of "do"
Luc, you mentioned in your post about a person's "ability to learn". I think Bryan may have hit upon a subtle message when he described the "willingness to learn". Most everyone is "able", but far fewer are "willing". Many people train very hard in Aikido, but come to the realization that the nature of the art makes it a very long journey. It sounds like your friend decided that he lacked the necessary motivation to make that journey. It happens. For some, it actually takes more courage to stop than to continue. For others, the opposite is true. The point is, it's not for everybody, and motivations, methodology and results will differ between individuals. Your friend may reconsider at some point, but I assume he thought out his decision at length beforehand, and if his "heart is really not in it", he has probably made what, for him, is the best decision. As for you, there will be other training partners. In fact, it's probably better that way. Keep to your path, and let others keep to theirs.