All the best, people. Oh, and one more thing, I thought I would share an interesting '90 minutes' fact that I came to know a few months ago, you know, just for the sake of it...

The following is an excerpt taken from here.

THE 90-MINUTE RULE EVERY SLEEPER SHOULD REMEMBER

Speak to sleep researchers and you will soon discover that most of them use a little-known trick to help them feel refreshed the next day. This is based on the knowledge that our sleep cycle contains five distinct phases, divided into four stages of non-REM (rapid eye movement) sleep, followed by a stage of REM sleep (in which we dream).

Each of these cycles takes roughly 90 minutes, followed by a brief interlude when we are relatively wakeful, before a new cycle starts again. This process is repeated usually for a total of four or five cycles a night. In other words, if we were to sleep completely naturally, with no alarm clocks or other sleep disturbances, we would wake up, on the average, after a multiple of 90 minutes.

This means that you will feel most refreshed when you awake at the end of a 90-minute sleep cycle because you will be closest to your normal waking state. To maximize the chances of this happening, work out when you want to wake up, then count back in 90-minute blocks to find a time near to when you want to go to sleep.

Let’s imagine that you want to wake at 8am and wish to go to sleep around midnight. Counting back in 90-minute segments from 8am would look like this: 8am>6.30>5.00>3.30>2.00>12.30>11pm...
In this example, you should aim to fall asleep around either 11pm or 12.30am in order to feel especially refreshed in the morning.