Why are we lazy to wake up early on some days, but on other days, how come we wake up early?

 

                    When our minds think that you've to go to school or office the next day, naturally it may think that as usual, you've to go. By thinking how tiring it is, our brain thinks that there's some danger the next day, so it's better to not let them go. Our brain comes up with methods to prevent us from going. Therefore after our sleep at night, we may feel not to wake up in the morning, but we may feel to sleep more.

But, if we think of any party, or new dress or any function for the next day, our minds think of it and long for it. Our brain comprehends that there's happiness on that day and our brain tries to wake us up as early as it can.