When Rabbi Yannai says that “in our hands we have neither the tranquility of the wicked nor the suffering of the righteous” (Avot 4:16), he notes the seemingly counterintuitive reality that the wicked experience tranquility while the righteous experience suffering.
The suffering of the righteous is part of their world, part of the pattern of their existence.
The assurance to the righteous is that they will “have no rest, neither in this world nor in the next” (Berakhot 64a).
This is no coincidence; it is a basic philosophical tenet – God bestows many favors and gifts upon the righteous, both in this world and in the next, but tranquility is not one of them.
Correspondingly, the Talmud states, “For the wicked, sleep is good for them and good for the world, but for the righteous, it is bad for them and bad for the world” (Sanhedrin 72a).
There is no rest for the righteous.
When a tzaddik wants to rest, God does not let him, as if to say that the lack of tranquility is an essential part of being a tzaddik.
–Rabbi Adin Steinsaltz