It doesn't sound like you have a sleep schedule whether you're on holiday or not. I use a computer for everything that I do also. Try setting a specific time to go to sleep and get up - don't sleep in just because you can that day. It takes a few days to acclimate but it's well worth it. For what it's worth, I got to sleep at 8:30 - 9pm and get up at 3:30 - 4am. I don't set my alarm on the weekend but still get up about the same time.