Fleas

When I was young, my father taught me how to kill fleas.

In college, a teacher told me that there were several ways of killing fleas (by that time I only knew the one my father had taught me).

Yet another teacher (still in the same college) taught me that one should not marry a single flea-killing method. Even if you did, he taught me even further, you should follow your method's rules, as you could loose sight of which method you were using in the first place.

I would like to teach you this, reader: one should not kill fleas, metaphorically speaking.