1. Ground Yourself. The most common reason for people thinking their lives suck is because they aren't living their own lives. Look deeply into how you are acting to please others- to please family, friends, and society. Realize, that you need to get to know who you are, what your needs are, and make the choices to follow your path. To know these things, a path of meditation and inner exploration is invaluable. What sucks is that you are not taking care of yourself.
2. Look on the inside. What are some qualities you have that you like about yourself? Are you funny? Are you intelligent? Are you sincere? Are you generous? What do you have pride in? Try focusing on the positive things in your life. You may be making huge influences to others even when you think you're useless.
3. Prove those negative thoughts wrong. When you find yourself in a bad mood, you could think of the negative things such as, "I'm dumb and annoying", "I'm better off dead", "I'm ugly, I wish I looked different", etc. Even though it's not true. Change your mind. Look for your good features, think about the ones that you know love you, look on your greater side. Realize that nobody's life is easy and that there will always be ups and downs, and moments of low self esteem. Don't automatically assume that nobody cares. Every person matters to someone. You're alive for a reason.
4. Appreciate what you see. Look in the mirror. Find some beautiful things about yourself.... Do you have nice skin? nice nails? beautiful eyes? full lips? Find stuff that appeals to you. When you can't change something, change your attitude towards it!
5. Determine why your life sucks. What can you do to make your life better? What do you desire to do? How do you want to feel? Make a few reachable goals and your own strategies. The first step is usually the hardest - getting help or admitting you need it.
6. Getting motivated. What motivates you? What gives you energy to go on everyday? Music? Love? Family? A 1km run? Jesus, Yahweh, Allah, Buddha? Your attitude? Your pet? Friends? School? Boost your confidence and determination by encouraging yourself into thinking positive.
7. Remember that some things can pass with time. There will be a tomorrow. There will be a next week. There will be a next month and perhaps by then, things will change. Everything is going to be okay when you think it's going to be all right. You are in control of your life and though it might get worse, it'll get better eventually. It's temporary and it will change much sooner than you think.
8. Think about happy memories. Whenever you feel like the future is 'hopeless', think about vivid memories. It will help make you feel better and that in the future, there will be good things, too. Happiness would not exist without sadness - it's like the yin and yang. They just don't exist without each other. Think about all the things you want to experience, feel, achieve. There will be many great moments in your life - don't let a few obstacles get in the way.
9. Don't stop yourself from feeling the joy. It's okay to step back once in awhile and just enjoy the moment. Even in tough situations - it's important to smile and laugh here and there. Don't restrict yourself from doing things you love just because you think you'll be criticized to do. Don't just leave memories behind, but don't try to live in the past, either. Let yourself enjoy life even if you're not at the best place you could be. You only live once - make the best of it.
10. Develop a gratitude journal. It's pretty simple. At the end of every day, write down five things that have made you happy or appreciative that day -- not necessarily big things, even small ones count. For example: nice weather, being praised by my boss for getting an urgent errand done, my playful dog, kids and hubby kissing me goodbye before they went to school/work, a hilarious joke a mate shared, etc.
11. If you feel persistently sad, unmotivated, anxious, hopeless or fearful, seek professional help. You may be suffering from a mood disorder or nutritional deficit which could be contributing to your situation. Remember there is always somebody there who wants to help you. You are valuable!

Source : http://www.wikihow.com/Stay-Positive-when-You-Know-Your-Life-Sucks