What things we can do to maintain a good mental health?

Theres a saying in Arabic that conceptualizes as follows;

A healthy mind is in a healthy body.

Now in order to sustain and maintain your mental health, at least read or solve critical problems that are not necessarily from a book, but critical problems can also be solved in real life situations. 

Thus, follows mere exercise where it moves your body in order to keep blood circulating in flexibly.

If you face mental exhaustion, take a walk (physical).

If you face physical exhaustion, take a brake (mental).

• Build relationships. Having good relationships with other people is the most important factor contributing to a sense of wellbeing. ...
• Exercise and stay healthy. ...
• Develop gratitude. ...
• Identify and use your strengths. ...
• Create flow. ...
• Give to others. ...
• Spirituality or religion. ...
• Seek help.
• Thanks to  ALLAH (GOD) What ALLAH Give you like health,whealth,happiness,Good name etc.
• Keep your wishes under your limit.
• looks sick people and thanks to Allah that you are healthy.
• Pray for Allah (GOD) ,you will get Good mental health.

meditation is my only answer.

before you are going to sleep. relax ,breathe smooth , the smoother the better. try to count your breaths. upper and downer movement of your lungs. try to remain still. don't let the streeses come into this zone.( but this needs a lot of expertise, and long guided practice)

with this exercise your mind will be as charming as a child.