Tanya Chapter 26 part 3

A person who rejoices in sufferings is called a lover of G-d and is rewarded measure for measure. Now, we move to understanding sadness that comes from spiritual disconnection. While truly, separation from the Divine is a reason to be sad, you still have to be happy. For this kind of sadness, you need will to make the time and have a calm mind. Once you have paid attention to your sadness caused by spiritual disconnection, the subsequent joy is powerful!