It is a very question u asked,that how can any one stay happy mentally.It is all in ur hand.U have accept few things -
everything is not in our hand.so we have to react rationally on each single incident.
Accept the reality and do things which is possibly done by u.
Dont stretch any incident, it will bring u sadness.
Happy in little things in ur life and enjoy those happiness with ur family and friends.
Always keep self confidence high.
Health Tips
for overall health
1.sleep 8 hrs at night.
2.avoid too much social media.
3.avoid too much use of mobile pc laptop.
4.avoid mobile pc 1hr before sleep.
5.before sleep may hear good music,or read a good book or can watch a good movie.
6.workout daily or regular morning walk or join gym.
7.Share ur thoughts with ur parents or good friends.
8.Concentrate on ur work,study,passion, hobby.
9.Maintain proper diet.
10.Take proper protein supplement and some time multivitamines.