I'm not asking this because I do not know, I'm asking so that I can get a feel for the people who post here. So I suppose that adding to the question should be"do believe that sticking to wholeheartedly is a must"?
Insha Allah I'll post my understanding of it after a few people make their comments.
Sunnat refers to an act performed by the Holy Prophet Sallallahu Alaihi Wasallam or his Companions. There are two classes of Sunnat:
a) Sunnatul Muakkadah - is an act which was regularly and constantly performed by the Holy Prophet Sallallahu Alaihi Wasallam and his Companions. A Person who regularly neglects it becomes a fasiq (sinner).
b) Sunnatul Ghair Muakkadah - is an act which was performed by the Holy Prophet Sallallahu Alaihi Wasallam and his Companions but was sometimes left out. A person who performs it receives great reward and neglect of it does not result in punishment.
Sunnah is how Rasulullah SAW explain what is in Qur'an. You Cannot just use Qur'an only as a moslem, but you have to learn sunnah too which is explained in Hadits Shahih or Hadits Hasan, then you will understand completely the way of islam. And then you just 'ittiba / follow Rasulullah SAW like all his companions did. That is the right way if you want to be a moslem completely. All his companions are the first and the best generation of moslem ummah.