Once, Reb Michoel Beliner, a spiritual mentor,'s son fell deathly ill. The doctors said that there was nothing they could do. Reb Michoel's followers advised him to immediately travel to the 3rd Chabad Rebbe, the Tzemach Tzedek. Reb Michoel began to weep, saying that he would strongly like to go, but the doctors said that it was only a matter of hours, how could he now set out on the road? One of the older chassidim berated him. He quoted from the Talmud that one should never despair of being granted G-d's mercy, and added that surely the good angels would succeed in having the Heavenly verdict postponed until he reached the Rebbe. And so Reb Michoel set out on his trip.
Arriving in Lubavitch, Reb Michoel was fortunate to immediately have a private audience with the Rebbe.
R'Michoel later related: "When I entered the Rebbe's room and handed him my personal request for my son, I thought to myself, 'The doctors said it's only a few hours...,Who knows what has in the interim happened with my son? ' and I began to weep. But then the Rebbe read my note and said, 'Don't cry. You must have bitachon in G-d with simple trust that He will save your son. Tracht gut vet zien gut. (Think good and things will be good.) You will yet celebrate the bar-mitzvot of your grandsons!' "The Rebbe said.
Soon after, the bo recovered. And from then on, whenever Reb Michoel experienced difficulty he would bring to mind the luminous face of the Rebbe as he spoke those words, and the situation would actually change for the better.
The Rebbe explains that when a person places his full trust in G-d, feeling fully at ease with complete bitachon, that is enough for him to merit G-d's salvation. This is true even for someone who is seemingly undeserving, for toiling in strengthening his bitachon, that alone gives him the merit to be helped. That is the deeper message of the words of the Tzemach Tzedek, "Tracht gut" - "Think good and things will be good."