In North America, senior citizens are treated poorly, as inconvenient liabilities. Almost everywhere else in the world, elders are revered. The later years of a person's life go unnoticed, and if it is noticed, they think they are looking at the end of a timeline. What they don't know and often neglect is the years that came before it. Here are thirteen life lessons from centenarians Clifford "Cliff" Crozier, Amelia Tereza Harper, and John Denerley, that stand the test of time.

1. Live for the day.

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Yesterday existed, tomorrow does not exist yet, and in between it all, is only today. What you do now will prepare you for the future. Do not place worry over things that have not happened because they have not happened. Until they do, you have your routines and your leisure to sort them out.

2. Age is only a number.

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The Scottish comedian Bill Connolly has said, "Acting your own age is about as sensible as acting your street number." Limitations come with age but they do not define who you are. Maturity is a choice. How you look at the world, how you change it, are your choices to make. Don't let your age define you or keep you from being who you are.

3. Make memories.

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Selfies are nothing new and unlike yesteryear, a photograph taken today is taken for granted. Phones didn't need to have the space for thousands of photos but now that they do, use it sparingly. A picture speaks a thousand words but being part of the moment is just as special as capturing it. Memories are stories you cannot duplicate. Make them something to remember instead.

4. Make much of time.

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Time flies when you're having fun. Time flies on autopilot when you're working hard too. Opportunity does not always come knocking on your door, so make your own. Be proactive in your decisions and learn to balance work and play. The sooner you devote yourself to your goals, the better you and the world will be.

5. Take care of your body.

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Processed food and fast food are not always avoidable and they're not always good for moderation either. Know what you put into your body and don't become a couch potato. Eat well, stay active, and you will feel happy for it.

6. Failure is not the end, it's the start.

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Nothing successful was always that way. To make goals a reality, trial and error is necessary. Sometimes months, sometimes years of it. Don't focus on the rejections or failures too long; learn from them and focus on that one acceptance. Remember, the squeaky wheel gets the oil.

7. Start small and think big. 

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We all have our inner circles, the people that are closest to us. Be it family or friends, don't neglect to ask for their help or consider their advice. It doesn't matter where you live or how much money you have. The real meaning of life presents itself when your caring for yourself turns into a caring for something more than yourself.

8. People never die.

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People handle their mortality in their own religious and reasonable ways. To the living, the deceased are their guide and to the deceased, the living are the continuation of a conversation. People do die, but they live on in their stories. You are history, so don't forget to pass it on.

9. Regrets, like mistakes, can be repaired.

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We always try to revise our stories, to make them more exciting and glamorous than they really are. Instead of trying to answer the hypothetical "what if," spend time improving what you can now. Acknowledge what you didn't do or did do, and learn from the experience to make a new and better experience.

10. Keep up with the times, but don't forget the times.

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The world changes faster more often than we can sleep. Before we know it, we wake up to some new replacement or technology that becomes a requirement. While the days of old are not too far away, adapting to the new world does not have to happen all at once. Slow and steady has always been a foolproof way of living, but don't be afraid to learn the curve; an email and a phone call is convenient but a visit face-to-face is courteous.

11. First comes happiness, then comes love.

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If you're not happy, find out what does make you happy. Satisfying the person you are is an ongoing journey, but once you know happiness, you can share it with someone else. Love comes after happiness. Happiness is when you know you're in love. In love with who you are, what you do, and everyone else who is happy too. Find your peace of the puzzle called life.

12. Be a source and be resourceful.

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The best way to find help for yourself is to start by helping others. Ask questions and answer questions equally. Admit when you don't know something and go near and far to find it out. No one knows everything, but we do know some things. Work together to learn as much as you can.

13. Keep moving forward.

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Don't stop thinking about tomorrow. If something or someone gets you down, turn yourself around, and rise up to the occasion. Accept your past but don't let it define the present or future. Think differently. Do it again. Progress can be made but it doesn't happen unless you keep moving forward.

We all are getting older, if we're fortunate enough, and if you get to be a day older, make sure you're a day wiser.