There are many ways to be happy but for me here are 5 ways how: 
1. Stay away from negative people or those who make you feel unloved and neglected.
2. Don't look on others achievements, focus on your own. You can make them as your inspirations but not as someone who can make you feel that your achievements are not that good enough, just because they were too far from what they have achieved already. 
3. Embrace sadness just for days and not for long. Always remember life goes on, so you have to continue and move on.
4. Cheer up someone on their down times even if you both feel the same way. Making a person feel loved and cared by you can help ease your sadness too. 
5. Accept that you're not happy sometimes. Life isn't about being happy always, it's all about finding real joy in times of sadness and agony.