Radak (6): Every Chasid says so in Galus.

Malbim: It is about pardon of sin.

Brachos 10b: One should not stand on a chair or stool or a high place when praying, rather, from a low place, for one may not act haughtily in front of Hashem.

Radak: Galus is compared to deep water.

Malbim: Omek is a depth, the opposite of a high place, e.g. an Oni, weak person or exile. It also refers to a low spiritual depth - one whose sin distances him from Hashem, who is higher than all heights, and his Nefesh stands in lowliness. Even though his bodily matters succeed and he is at the top of the world, "I called to You" from two depths - of the body and of the Nefesh ¹ .

Lev Eliyahu (Shemos p.83): He calls from two depths. (a) He sees that due to his sins, his heart was blunted, and the senses of his Nefesh weakened. He wants to be good, but he feels that his Nefesh is incarcerated. He calls to Hashem "Hotzi'ah mi'Masger Nafshi!" (142:8) (b) He recognizes the grandeur of the Torah, far more than he knows, and calls to Hashem to help him to understand it!