Ok, so if I remember it correctly:
The part of Kosh that was in Sheridan told him to jump because he knew that Lorien was in Z'ha'dum. Sheridan jumped and is grabbed by Lorien. After he replied Lorien's question correctly (why do you want live or something similar), Lorien released Sheridan only to fail to grab it again. Sheridan died and Lorien had to pass part of his live to Sheridan.
So, why did he have to release this character only to try to grab him again and fail? I dont understand it.