Pirkei Avot 1:14

"He [Hillel] used to say, if I am not for me who is for me, if I am for myself what am I, and if not now when."

The traditional interpretation of this mishna is that we are permitted, even comanded to look out for our own interests, but we must also look out for the interests of others.  However, the Mesorah Publications version of Pirkei Avot offers an astonishing interpretation of the first clause of this mishna: that it does not mean merely that one must look out for one's own well-being, but rather that one must be responsible for one's own spiritual development.  This a a much more profound interpretation than the common one, that one must care for others to care oneself.  The focus of all of Pirkei Avot is the importanct of spiritual development through Torah.  If the Mesorah interpretation is correct, then the second clause, that looks to others, must also be read to mean that we are responsible for kiruv, for outreach to others.  The last sentence requires that we not delay in our own spiritual development or the of others.  If we do not start today, we will be delayed in remaking ourselves and other in a more spiritual path.