These are the sorts of things that I find best covered by "Vertical Mapping". Although this topic is not thoroughly covered in the GTD book, it is pretty much half of David Allen's GTD Roadmap seminar. Basically, it goes a little something like this...

Vertical Mapping is the process of connecting all of those N/A's (Runway) and Projects (10,000 ft.) to your responsibilities (20,000 ft), goals (30,000 ft.), Vision (40,000 ft.) and Principals (50,000 ft.).

In your example, "learn to be more compassionate" might actually be a mid term goal (12 to 18 months) that is part of your "responsibility to humankind" that has a project of "daily random acts of kindness" that has the next action of "Give a bum your lunch money".

I have a further explanation of this on my blog.

I am really surprised that David himself has not written more on this topic because this, in my view, is the real meat of GTD. It gives every next action a direct connection with your life's principals and goals. The vertical map is all about the why of getting things done on a very deep personal level.

I regularly review my Vertical Maps while reviewing my projects and next actions and if there is an action or project that does not fit in vertically then I really have to force the question why that action/project is really on my list. If it is not directly related to the 50,000 ft. of who I wish to be then I can tell you it's likelihood of getting done (zero).