sattava is upper level,rajasa in middle,thamsa lower

urdham gacchanti sattvahastha,madhya tistanti rajasa,
jaghanyguna vrttisthu,abho gacchanti tamasah---18

Those who establish in goodness rise upwards.The passonate remains in the middle[regions].the dull steeped in the lower occurences of the modes sink downwards.---18
The human body is like a cross road.who stayed in sattav guna[goodness]goes to higher level from human body.like god goddess,angles.But who stays in rajas gunna stays in center as a human being.In lower level guna thamsa goes to levels as plants,stones,devils,etc.this is our state after death as described in gita.
But if we are free from gunas we do not go anywhere but becomes one with the self[God].this is self realization in this body and afte body we remains our being.so formation of body is due to these three gunas.when in human body we realize sat-chit-ananda.this is our destination.