How to Be Healthy and Happy

Focus on the positive: Positive thinking is an essential step in developing a happier mentality. Instead of focusing on the negative, shift your emphasis to the positive. Try not to criticize yourself. Reframe any negative thoughts you have about yourself into a good statement. For instance, if you're thinking, "Instead of saying, "I can't believe I'm so stupid," say, "I'm brilliant!" I can learn anything if I set my mind to it!"
If you make a mistake, consider it a learning experience.

Please don’t compare yourself to others: It’s easy to make a side-by-side comparison between yourself and your peers due to social media. Know that public lives may not reflect their personal lives. Be grateful for what’s good in your life instead of what’s good in others. You can use comparison as a motivation for self-improvement.

Manage stress in life: Stress may have an impact on both your mental and physical health. 
It can produce anxiety, irritation, and hostility, as well as headaches, muscular discomfort, weariness, and sleeping difficulties. Consider what activities you might eliminate from your life to reduce stress.

References
https://www.wikihow.com/Be-Healthy-and-Happy