Notes

I'm a big fan of Bhagwad Gita and I like the way of living described in it. In my opinion the teachings in that book is the simplest way to make life simpler.

To answer the question, life can be made very simple by eliminating two elements from your life:

1. Expectations
And
2. Attachments

Give it a minute, think about it. Everything that is happening in your mind and around your world, which troubles you, makes you worried and adds complexity to your life, has its roots in only these two elements.

Expectations.
You can't eliminate them altogether, but you sure can try to minimize it. Don't expect help from other people. If they are helping you in some way or other, be thankful n grateful to them. But if they aren't/can't help you, never mind. It's not their duty to help you. You are, in no way less capable than them. If they can help you, you sure can help yourself.
When you help someone, don't expect anything in return. Not even a "thank you" from them. The motive behind helping should be your own peace of mind. Help only if that makes YOU feel better, and not because you think, they might return the favor someday.
Remember, if you help someone and want something in return, then its not a "help", its business.

Attachments.
It is the single most powerful factor which can throw your life into chaos. When you get attached to a person place or thing, your happiness and sorrow, peace of mind and mood depends entirely on that particular entity. Attachment to a person: your mood for the entire day will depend on how that person behaves with you. He /she talks nicely, you're all happy that day. If he/she doesn't/couldn't talk to you, you're probably going to waste an entire day over thinking and analyzing what went wrong, why that person is avoiding you.
It took several billion years for your brain to evolve, please for the love of God, don't let others control it. If they talk nicely, you reply them politely. If they talk rudely, keep your mind calm and at peace and walk away. If they don't talk at all, that's fine. You've got your own life, enjoy it. Remember, you probably didn't know that person few days/months/years ago. And you were fine then. In these years or months you got attached to this person and developed expectations. That's why you're losing your peace of mind. That's why your life isn't simple.
Your happiness and your state of mind should depend only on the things which you can control. Like what ?
Like your work. Work on something that makes you happy. Help someone if that makes you happy. Always be in total control of your life. Don't give the remote control to others.
Life is always simple. Like 1+1=2.
We integrate and differentiate several variables and make it complex. Because it gives us an illusion that we too are important.