My husband bought The Four Agreements for me about 10 years ago and I often think of it in my day to day life...just remembering one of The Four Agreements in a given situation can help me not get caught up in the "stuff" that doesn't matter. We tend to be self-limiting, self-judging and we focus on the wrong things....this book will help you move past that and give you some important tools to start experiencing freedom and true happiness.

The book is definitely worth reading in it's entirety, but these are The Four Agreements that the book goes into detail about...

Be Impeccable With Your Word: Speak with integrity. Say only what you mean. Avoid using the word to speak against yourself or to gossip about others. Use the power of your word in the direction of truth and love.
Don't Take Anything Personally: Nothing others do is because of you. What others say and do is a projection of their own reality, their own dream. When you are immune to the opinions and actions of others, you won't be the victim of needless suffering. (...this one was hugely life-changing for me.)
Don't Make Assumptions: Find the courage to ask questions and to express what you really want. Communicate with others as clearly as you can to avoid misunderstandings, sadness, and drama. With just this one agreement, you can completely transform your life.
Always Do Your Best: Your best is going to change from moment to moment; it will be different when you are healthy as opposed to sick. Under any circumstance, simply do your best, and you will avoid self-judgement, self-abuse, and regret.

We have a choice. To suffer through life and be unhappy... or to enjoy life and live true happiness. My choice is happiness, what's yours?