Early Morning

Here I sit at 6 am. I woke up at 4:30 am and couldn't fall back asleep. I know I went to bed early last night, but this is early even for me! Why is it that on weekends I have a hard time sleeping in? I always feel like I'm going to miss out on something fun. Yet, on weekdays when I have to get up early, I have a hard time getting out of bed. Must be a psychological reason - just haven't figured it out yet.