4 or 8 hours... is it always 4 or always 8?
your unstable sleeping hours will caused you to be tired also leh...
sleep at least 6 hours constantly should be a good start... of course lar if you can sleep 8 hours EVERYDAY will be the best. But then nowadays i doubt it
even me also sleep like 5.5 - 8 hours daily only. Never fully 8 ler because I am a 'nite ghost" hahahahha