Azorín "El Escritor": help with sentence =D

I am having trouble with this sentence. It is not an easy one and was hoping that someone could help me out and give me a little insight as to what this sentence means and how it should be translated. ;)

It is a line from Azoín's "El Escritor". Here is some context to go along with the sentence with the one in question in blue.

Cincuenta años escribiendo... Desde los tres quinquenios con la pluma en la mano. Impetu, fervor, perseverancia, entusiasmo... Ha pasado mucho tiempo y los años cargan sobre mis hombros... Todo lo que asciende, desciende... Cuando podemos ya esperar, habiendo visto correr tanto tiempo lo ciframos en la obra cumplida.

Thanks to all in advance for your help :D