The scientific study of mind and behavior is called psychology.(Ref: www.simplypsychology.org) So why is it important to study the mind psychology? It is because it's our mind that is taking the decisions and accordingly we tend to behave. The healthier and happier the mind, a positive impact on our behavior and happiness in our life. The happier you, all things happening around you are good. Good things give us deep satisfaction and it is this satisfaction which psychologically effects our mind in a productive way.
The mind easily takes the negative things happening around us and it results in our negative behavior. The negative feelings include, fear, jealously, anxiety, stress, depression, bad dreams etc. etc. All these impact our health and body in very bad manner and keep us away form being happy.
So its really important that we constantly train our mind to be optimistic, helpful, hopeful and constructive. How to we make a positive psychological effect on our mind?
Meditate: Meditation is a proven technique to calm your mind and give you a feeling of content. No stress on mind is a simple way to mental well being.(Ref: www.healthline.com)
Be constructive- Engross yourself in doing something constructive. May be pursue some hobby or do some creative work in your professional life.
Be Kind- Show kindness towards others and help them, doing something for others creates a really happy feeling inside you and that boosts your positivity of mind.
Stay away from negative people - This helps a lot. Try to be around people whom you like and who give you a good feeling. Who help you motivate and make your think optimistically.
Read books - Read motivating books or books on how to keep yourself happy. (Ref:https://www.happinessfollower.com/happy-moments)
Conclusion : It is really important to have a healthy mindset, to keep your body and mind working in a good condition for you. Life should be about having fun and happiness and not negativity.