The past self is there to be surpassed.

$$\oint_{w=0}\frac{dw}{2\pi i}\frac{1}{f(w)-z}=\sum_{n=0}^\infty\frac{z^n}{n!}\left.\frac{d^n}{dw^n}\left(\frac{w}{f(w)}\right)^{n+1}\right|_{w=0}$$