Some of the most famous images of Passover — the belted tunic, the shoes on the feet, the staff in the hand — were never meant to continue. Targum Pseudo-Jonathan on Exodus 12:11 states it bluntly: "according to this manner you shall eat it, this time, but not in (other) generations."
In other words, the ready-to-run posture was for the first night only. Future generations would eat the Pesach reclining, not standing. The running clothes belonged to a people about to flee Egypt. Once Israel was free, the meal would take on a different character — leisurely, deliberate, conducted as free people who did not have to hurry.
The Targum also supplies the reason for the haste on that first night: "because mercy hath been shown to you from before the Lord." The fear in which they ate was not a fear of punishment. It was the fear that accompanies a miracle in progress. Israel was standing inside a deliverance that had not yet finished unfolding. The proper response was awe — dressed for travel, eating with reverence, ready to move.
The rabbis later built the reclining posture of the seder directly against this one-time command. Because the first Pesach was eaten in a hurry, every subsequent seder is eaten at ease. The posture itself becomes a declaration of freedom.
Takeaway: The first Pesach was eaten on the way out. Every Pesach since has been eaten as proof that we have already arrived.