Some people retire and become depressed because they have a hard time finding ways to fill their lives with activities that interest them. Others, retire with a lot of projects that they now have the freedom to pursue. Circumstances change as we get older and some people find it difficult to adjust to some of the changes and losses that occur. Other people find joy and excitement in spending more time with family and grandchildren, if they have them, activities they did not have enough time to pursue before and/or new projects that inspire them. I think the difference depends on the person's personality, view of life, state of health and social connections.

People become grumpy as they get older because as we continue to experience life as we age, we also experience hardships, death of loved ones, financial loss, health issues and such. People will tend to focus on ALL the things that have gone wrong and soon the "Victim Mentality" kicks in and becomes very strong. Especially if life goals were not achieved and an individual is getting older and older they will tend to just focus on how hard it is, how they have been hurt or cheated out of life. All they really need is a strong reminder of all the good and how they are loved. =) Hope this answers your question! You can learn more about mental vibrations here:
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There is a veritable cornucopia of answers to the question of why some people become grumpy as they get older. One of them has to do with the stress of challenges, which are hurdles to jump over for some people and barriers to trip on to others. Stress brings out the best and worst in people. Aging is a stressor. Thus people who have been happier in life become more content and conversely, people who have been frustrated and negative, become grumpier.

Self-knowledge can teach us how to reinterpret negative events and how to turn them into positive experiences. How we think about life is as important as what happens in life. Therefore, one key to happiness in old age, is self-improvement in ones life as we move along through the different life passages.

Take Nietzsche’s word’s in Victor Frankl’s book, Man’s Search for Meaning: “If you know the why, you can live any how.”

Most people do not realize the power they have over their own lives. When things dont go as planned they begin to harbor blame, regrets, and other negative feelings rather than recognize that they always have the power and choice to choose their own experience. Many in that position see the world circumstances as something that happens to them rather than something they create with their own actions and beliefs and do not realize that they have the power to choose something different whether it be the circumstances or their own reaction to it.

"Between stimulus and response there is a space. In that space is our power to choose our response. In our response lies our growth and our freedom."
-Victor Frankel,
Psychologist and concentration camp victom

I think if you're content with life and you have more or less achieved everything that you wanted, you are more likely to be happy. Sadly though this is not always granted to everyone. Also, if you have good friends and a hobby you will have something to occupy your mind. If you're just sat at home all day alone watching four walls you can see how easy it would be to become depressed.

I don't think every one its usual to all.