People make their own reasons for being unhappy. It is observed that most people do more to remain unhappy rather than to feel happy. There are few generic reasons which make most people unhappy.
From the below link, find out the top reasons that makes people unhappy.

It’s difficult to remain a positive thinker when you’re stuck indoors in the middle of winter and, with me being a home worker, it’s doubly so as I don’t go out into the fresh air and walk around as much as I should, relying instead on a bit of exercise via my Wii and fresh air through an occasional trip down the garden to feed the birds or put rubbish in the bin.

Do you feel sad, angry, resentful, or discouraged? With a little effort, you can turn your life around. You really can become happy again. How? This article takes you step by step through the process of learning to live in the moment, how to practice being satisfied, how to use prayer and meditation to lift you up, how to play and, perhaps most importantly, how to stop trying to fix other people. This last step, alone, could make a tremendous difference in your outlook on life. Learn how to include these steps in your daily life, and bring joy back into your heart.