Starting the day correctly starts the night before. With Sleep.
I am not a sleep expert and have not significantly studied the science of physiology and sleep. All I can tell is that for myself - and for everyone else I know - sleep is a crucial aspect to the following day.
The amount of sleep required by individuals varies and I don't know why. I've known people who could subsist on 3 hours a night quite nicely. I've known people who absolutely require 8 hours of sleep a night at a minimum and are a wreck between.
Many of most (most of us, depending on what survey you see) are sleep deprived. I didn't really used to accept this - for years I lived on 4-5 hours a night because I had lengthy commutes and I wanted to have a life - but realized that I had all the classic symptoms: tired during the day, making up lots of sleep on the weekends.
Sleep matters because being rested matters, because starting the day rising up refreshed is far different than starting the day dragging yourself out of bed:
1) Find your sleep amount: I suspect most people need more than they think. A classic method is to start at 8 hours a night, then cycle back a half hour at a time until you find your limit. This becomes the minimum amount of sleep a night you need. It will be different for other people. Accept this.
2) Keep your sleep amount: Once you've determined the minimum amount you need, assiduously guard it. If your rising time is 0500 and you need 7 hours of sleep, you need - NEED - to be in bed, asleep, no later than 2200.
You'll find excuses of course - I always do: "I'm not tired yet" or "Just five minutes more to do this". The reality is that every excuse you make deprives you of the ability to start the day out right. Keep your sleep schedule the way you keep your important meetings: inviolate and on-time.
3) Sleep when you sleep: There is a multitude of sleep resources on the Internet so I'll not belabor the point. Just make sure that when you're asleep, you stay asleep. You'll find the things that cause you to be disturbed during the night. To the greatest extent possible, fix them. It's a matter of both quantity and quality.
The best guard against a bad start to the day is to insure that night before was one that allows you to rise fully rested and refreshed to meet the day. The day's struggles will be enough. Don't compound them by being run down yourself.