Sometimes very simple techniques are the most powerful.
Each morning the minute you wake, write down three things in this day you have to look forward to. If you are having difficulty doing this, look for very simple pleasures, like: having a cup of coffee or tea, playing with your pet, experiencing a sunny day, reading, or talking to a friend.
Each evening at the end of your day, write down three things that were good today. They might be things you are grateful for, like your health, a friend, or a meal. Or you might think of highlights in your day. Perhaps something lucky happened or you received a compliment.
These techniques may seem too simple to work, but they are actually perfect for helping you change your focus. While you are thinking of good things in your life, it crowds out the thoughts that are making you depressed. And by choosing things to look forward to in this day, you notice and appreciate them much better when they come. Happiness does not lie in circumstances as much as it does in our thoughts. There are wealthy people who are terribly depressed, and poor people who are happy. There are some who feel lonely even though they are surrounded by loving family, and others who live alone who feel blessed by the love in their lives. Some people have lost so much in their lives, and yet live each day overflowing with joy, because they focus not on what they have lost or don't have, but rather on what they do have.
It won't take long for you to see that these two simple techniques improve your moods and happiness the more you practice them. If you like them, start adding new moments to your day. You could for example, think of three reasons to feel good about yourself each day, or each day answer how you know you are loved.