I always stay awake on eastbound day-flights.
I wish there were more flights to the far east that left mid-afternoon. I don't understand all these late night SIN/HKG etc flights - you end up having a full night's sleep and then arriving in the evening when you should be going to sleep again but can't.
If you leave mid-afternoon you only get a partial sleep and then arrive in the late morning so there's enough time to feel tired by the time the evening comes around.