How do you hold a mountainbike handlebar properly?
The most important rule when riding in technical terrain is to remain relaxed.
Only then, can the 80 cm or more of travel that the human body is capable of providing be effectively added to the 10 - 20 cm of travel the bike provides. If the body is cramped up, the suspension travel it can provide is reduced and can no longer be used to its full potential. The dynamic human suspension travel can, with advanced riding techniques, even act early, such as with the bunny hop or pre-hopping over take-offs in order to land on the downramp rather than overshooting into the flat.
The 'sucking-up' of bumps or even entire jumps or doubles - a technique used in BMX riding - belongs in this category also.