Adapted from a shiur by R' Shlomo Farhi, sent to me as a guest post by Nosson Gestetner of http://gtorah.com:
The Gemara relates a story about a gentleman called Nachum. He was a man who had a a difficult life, but whenever something bad happened, he would say "Gam Zu L'Tovah - this also is for the good", and this is what he later became known as - Nachum Ish Gam Zu. But why does the Gemara call him Nachum Ish Gam Zu, literally, “Nachum Also”? He was famous for saying "Gam Zu L’Tovah" yet he is not called "Nachum Ish Gam Zu L’Tovah"! One would think that "L’Tovah" would be the key part of what he is remembered as, as opposed to the seemingly extraneous ‘also’.
To understand the answer, we must be aware that there is a fundamental misunderstanding with regard to what he did, and consequently what he is remembered for until today. He wouldn't pass a car crash and point and say it was “l’Tova” - one cannot label an inherently bad thing as "good". "Good" is clearly not an applicable adjective. The depth behind his words is as follows: What he did was recognise the masterplan of Hashem, and the web in which events in our lives unfold. He attempted to see the bigger picture, the greater good which is hidden from our direct sight. That web, that bigger picture, is l'tova. Parts of it may not be, or may not obviously be but in recognising that bad events are part of a good web, we should be able to say "Gam Zu L’Tovah!" So in fact ‘Gam Zu’ – his ability to see that this is "also (one more event)" is the key part of what Nachum said - it is the mechanism by which he could label bad as "also" being good. Not just "L’Tovah".
It take a great inner strength to truly be able to say, in the face of a bad event ‘this too shall pass’ and to really believe in the bigger picture and the greater good. But by working on that strength, we will be able to get to the stage where we can say, as Nachum did, Gam Zu L’Tovah – This too is for the good. The word ‘also’ is the very mechanism that allowed him (and resultantly us) to state something was ‘L’Tovah’.