- Make sure your body is in a good health in every possible situation(suitable food, proper exercise, comfortable sleep, grooming and other things). most of the time that I become sad/angry/depressed/disappointed, I find it's because of my body condition. take care of it in a best possible way.

- Have people around you that you know they care about you and you have a place in their life.(like family, friends, bf...)

- Think about your dream job, work in a field that you love the most, after all, you want to spend most of your time in your job, so choose it based on what you love to do the most and your talents.

p.s. Also you may like to look at human's need Hierarchy theory(it's good, but remember it's still just a theory): 

https://en.wikipedia.org/wiki/File:Maslow%27s_Hierarchy_of_Needs.svg
 

p.s.2. I like aegis's suggestion list.

(Not all Americans are religious.)

Yes, I'm happy. I'm the only person who can decide whether or not I am happy. That being said, there are certainly some external factors that seem to make it easier to be happy. Here are some random suggestions, knowing nothing about your situation:

1) Find a bf and tell him it's his job to make you happy.

2) Exercise regularly.

3) Eat properly.

4) Even if you're not sleeping well, try to keep regular hours in bed.

5) Reward yourself for getting through such a hard time in life.

6) Do things with your friends and family.

7) Bathe regularly and take good care of your health.

8) Maintain a regular routine.

9) If possible, reduce stressful things on your schedule.

10) Think of all your accomplishments, smile and laugh.

Whatever you are struggling with, just know that others care about you and want you to find inner peace and to be fulfilled as a person. Look for friends that are people who care more about people than they do about things, because materialist pursuits will eventually burn you out and wear down your friendships. 

Also, I respect you if you don't think religion is for you, but I just want to say that you have to somehow know that you are loved to be happy, to have a reason to live. That's why Jesus makes me happy; I know He loves me and it is something that can never be taken from me. That's honestly what has helped me, but again if you are past religion like many people are, then just know too that others care about you and want you to be be at peace with yourself.

 I think you need a purpose in your life. People always get lost when losing life/work purposes.

Try to arrange schedules both in the long run and in the short run. Do what you like and what you should do just following your schedule list.

You need a challenge in your life. Something with a goal that you can achieve