Imagining He Died and Returned to This world to Rectify Himself:
Rav Shmelke of Nikolsberg zy”a (Sefer Divrei Shmuel) says that the reason we wear a kittel by the Seder is because it is the clothing worn by the dead. He explains that it is meant to bring a person to imagine that he has already passed away and is being shown all his sins and judged in the World of Truth. If a person thinks about this, he will certainly be inspired to repent and improve himself and to serve Hashem properly from now on.
At the Seder, the kittel brings a person to imagine that he has already died and been shown all his sins, and then given a second chance and sent back to this world to rectify all that he did wrong. This should cause him to be joyous and happy and to thank Hashem for giving him this new opportunity to serve Him and reach higher levels of ruchnius.
More Than Enough Maror:
One year, there was not enough maror at the Seder table of the Ahavas Yisroel of Vizhnitz zy”a for all of the people. One of the chasidim called out to the gabbai to bring more maror but the Rebbe said, “The Jewish people do not need any more maror. We have had enough!”
Shemonah Esrei in the Middle of the Haggadah:
Sefer Admorei Belz (Chelek 3, page 206) relates that the minhag in Belz was that after the Rebbe concluded his Seder, he would go out to the streets to hear how the local Yidden were conducting their Seders.
One year, Rav Shalom of Belz zy”a and his gabbai, R’ Elimelech, heard a man make the bracha of “Ga’al Yisroel”, and continuing with the tefillah of Shemonah Esrei. The gabbai laughed but the Rebbe said, “This man accomplished a lot with this tefillah. He has no children but he will now have a baby!”
Emunah is Greater Than Seeing:
Sefer Siach Zekeinim (Chelek 2, page 186) relates that one Pesach, when Rav Yissochor Dov of Belz zy”a reached “Shfoch Chomascha” he sent one of the children to open the door for Eliyahu Hanavi. When the child returned, the Rebbe asked, “Did you see Eliyahu?”
The child answered, “No.”
The Rebbe’s grandson, Rav Yochanon Twersky zt”l then asked, “Is it really true that one can see Eliyahu Hanavi?”
The Rebbe answered, “Yes. He can be seen. But someone who believes without seeing is a lot loftier than one you sees.”
He quoted the pasuk (Shemos 14:31) that says: “And Yisroel saw...and they believed”, and said that even though they saw the miracles with their eyes, and they did not need to have emunah, they still had blind emunah in Hashem.
This idea also explains the pasuk (Bereishis 15:6) that says about Avrohom Avinu: “And he believed in Hashem and it was considered for him as an act of tzedakah.” This can be understood to mean that Hashem lifted Avrohom up to the Heavens, and he saw everything, but he still had simple emunah in Hashem, and this was considered an act of righteousness.
Washing the Face to be Able to See:
Haggadah Meor Tzadikim (Skver, page 383) relates the following story:
When Rav Itzikel of Skver zy”a was a young boy of 4 or 5 years old, he met some of his friends on the first day of Pesach. One of them told him, “I saw Eliyahu Hanavi at my Seder. Did you see him at yours?”
The young Rav Itzikel was struck with a strong yearning to see Eliyahu Hanavi as well. He went to his father, the Magid of Chernobyl zy”a, and sadly asked, “Why can’t I see Eliyahu Hanavi like other boys can?”
His father told him, “You need to wash out your eyes.”
The boy took his father’s words literally, and he went to wash his eyes... but he didn’t see Eliyahu Hanavi on the second night either.
He went back to his father with tears in his eyes and said that even though he washed his eyes, he still couldn’t see Eliyahu Hanavi. The Magid told him, “Wash them for as long as is necessary until you can see him.”
His intent was that one needs to purify his eyes completely in order to see Eliyahu Hanavi.
Years later, when Rav Itzikel would relate this story, he would say, “I washed and washed and washed and by now I believe that I can say that I did see him.”