Chasidic teachings differentiate between two levels of loyalty and devotion to G-d: an Imposed devotion and an innate devotion. The first kind is experienced by those who are filled with an awareness of "self", a feeling of being independent from and outside of G-d. Yet, through study and contemplation, they come to the recognition that it is logical and good to devote themselves to their creator, who is infinite.
They therefore overcome the "self" and devote themselves to G-d. But the independent "self" remains intact; it is merely suppressed.
A higher level of devotion, usually associated with the saintly, is an existential and innate devotion, one in which there is no "self" that needs to be overcome. Such a person is not susceptible at all to sin.
When we sit down, our heads are brought to a lower position. This symbolizes a partial bowing to the Divine, since the head is not completely lowered. But when we recline, our heads are nearly if not completely lowered. This symbolizes an absolute and innate "bowing" to the Divine.
On the night of Pesach we all recline: Because of the intensity of the Divine revelation that occurred on this night, and which reverberates each year, kulanu mesubin, we all recline--we are all imbued with an innate devotion to the Divine.
This fleeting revelation that overwhelms us on Pesach gives us a jolt, a jump-start for the work of refining the "self" during the forty-nine days between Pesach and Shavuot.
—Haggadah for Passover