Absolutely essential to get all the downhaul off, mast spanner centered ( think wing section and with the spanner facing down, any lift from the wind will be toward the water and not upwards ) and travellor off, but even more essential is to get the boat correctly aligned with the wind, ie the mast perpendicular to the wind. Oh and did I forget that the mast must be totally sealed from water ingress, even just a few litres of water at the tip and you will not get it past the mid point.

There is one time where everybody struggles though, light winds and very flat water, there is enough stiction between the sail and water that the tip just doesn't seem to want let go. I was on rescue duty a wee while ago and a Hurricane 5.9 with the latest fat head sail couldn't get the tip out, even lifting it from the boat was quite difficult, but as soon as the sail broke away from laying flat on the water, it was a doddle.