Brochas Daf Chof Ches amud beis

And when R. Yochanan ben Zachai took ill, his students entered to visit him. When he saw them he began to weep. His students said to him: light of Israel, "right pillar", mighty hammer, why do you weep?

The Gra explains the allusions embedded in the names gives R. Yochanan ben Zachai by his students. Chazal tell us that the world stands on three pillars, Avoda (the left pillar), Torah (the central pillar) and Gemilus Chasodim (the right pillar). Of these, post the destruction of the Beis HaMikdash (caused by our sins) the two former no longer exist (at least to the same degree): the third "right" pillar remains complete, and because of this, it is the only one still designated with the name pillar.

Ner Yisrael (light of Israel) is an allusion to Torah, which according to the posuk in Eicha (2:9) "her king and her princes are among the nations: there is no Torah" has been eliminated/(damaged?) post Churban. Meanwhile "mighty hammer" refers to Avoda, which the Gra informs us is achieved by overcoming our Yeitzer Hora and destroying it as with a mighty hammer.