"My word, Severus, that I shall never reveal the best of you?" - Albus Dumbledore
The Hanged Man is a card about the clarity and understanding that comes from surrendering. By "letting go" of a stubborn situation and coming to a standstill, one is able to view the whole picture from a different perspective, and thus come into new insights. In order to gain the wisdom of this card, sacrifices may have to be made of seemingly important things that turn out to be the key to release the puzzle.
Severus Snape is certainly a very "suspended" man - much of his life hangs from the pivot point of his betrayal of his service to Voldemort. Due to his love for Lily, Snape willingly undergoes grave danger as a double-agent in the face of resentment and suspicion from both sides. The strength and extent of this sacrifice comes as a surprise to Harry - and many others - who had thought Snape a traitor. Instead, it turns out that Snape had worked for Dumbledore's cause ceaselessly to his death.