ROTS and the prequels had a lot of silly things going on with the Jedi. I think Lucas was going more for a celibate monk sort of thing. They should have no possessions beyond their lightsabers and cloaks, which is why Anakin gives Artoo to Padme, right? I think that was mentioned in the ROTS novelization. This is also an idea given by Obi-Wan in the original Star Wars novelization and in the radio plays, that Jedi don't need money or possesions, they give it all up in order not to be bound by materialism. Also you can't see your family, which is why Anakin is never allowed to go see his mother over all those years.

The PT kind of turned the Jedi into jerks in some ways, they go around, take kids from their parents and never let them see them again, indoctrinating them and training them. They are not allowed to love, not allowed to be bonded with their family. Total disconnect from everything. I really like the Jedi as dipicted in the Tales of the Jedi comics much more than the PT monastic order.

Anyway, that is what Yoda was talking about, not to be bound emotionally. Another part of their philosophy is moving onto another plain of existance, therefore death should not be mourned, because while they are lost to us, they are not gone completely, they just went into another room as it were, where we can no longer see or be with them.