We cannot be happy all of the time, but we certainly can be more fulfilled than others if we are having a positive attitude towards life & we handle all of the situations in life with rational & positive attitude. Happiness is not much to do with material goods or high achievements in life, rather it is all about our outlook on life.
Here below are few points which needs to be considered for happiness in one's life:
1) Believe in yourself. Your inner strength is your Soul strength, Mental strength which comes into action in your hard times, which defeats all of your negative symptoms of sadness, depression etc. in your life. In hard times your self confidence builds your low esteem. When you are passing through bad times, you have a feeling of self dejection & a feeling that you have lost all in life. In all such times, your Soul strength comes into play & if you believe in that inner Soul strength then you can easily over come all of your negative traits & can feel happy. Bhagwat Gita teaches us that we are a Soul which is indestructible & is having infinite powers in it. Problems in life, how big these may seem are too small in front of the infinite powers of your Soul. So believe in that Soul & it's inherent infinite powers. As our Soul is a spark of the Infinite, all powerful, all pervasive Universal Soul, so it's powers are also limit less. This soul present inside our human body, in fact gives strength to our mind to carry out all difficult tasks. Believing in oneself is nothing but believing in one's inner Soul. All fountains of knowledge & strength come out of this inner Soul only.
"You really have to look inside yourself and find your own inner strength, and say, "I'm proud of what I am and who I am, and I'm just going to be myself." Mariah Carey
2) Appreciate what you have: We generally do not appreciate the positive aspects in our lives. Our nature is to ponder on the negatives & what we don't have in life. To us others grass always seem greener. In fact we should appreciate what we already have. That shall give you a strength that at least you have been able to achieve that much. Do not compare yourself with someone very rich & with much more facilities & resources than you. Just see how good you are from those who lay a life along roadside without even having a roof over there head. We should be grateful to God for whatever we have in life. If you are able to thank God for, whatever, He has given you in life, then also you shall appreciate what you have in life. We should always focus on the positives in life. So let's start appreciating what we have. Appreciate what you have achieved in life till now. Appreciate your own looks & body. Appreciate the house you live in. Appreciate that you & your family are having good food while there are many who are not just having that also. Appreciate your loved ones, your children. Appreciation of yourself shall bring confidence in you, it shall also bring peace & happiness in your family life.
3) Have positives in your life: Just have positive traits in your life & you shall feel happy. Having a nature of Forgiveness shall remove unnecessary tensions in your life. Showing Gratitude towards others is also a positive aspect in life as it makes you humble & creates an environment of peace & harmony in your life. Have smile on your face & laugh a little in your life as it makes your mind cheerful. Don't be dormant in life & be physically active as active people are the one's who feel happiness in life.
4) Be peaceful in mind: To be peaceful at mind, the first & foremost thing is to be satisfied with what you have at present in life & try to make harmonious relations with the people all around you. Once you are able to do that then you shall find that you are better off & much peaceful. Other than this do little prayer daily to God & if you are able to find time then do little meditation daily, as meditation makes one's mind peaceful. Here below is a verse of Bhagwat Gita & as per that let's control our desires & let's not hanker after these desires. One who is able to control his/her desires finds peace in life & with peace comes happiness in life.
samudram apah pravishanti yadvat
tadvat-kama yam pravishanti sarve
sa shantim-apnoti na kama-kaami” (Gita: Chapter II verse 70)
"As the waters (of different rivers) enters the Great Ocean, which though full on all sides remains undisturbed, like wise a person who is not disturbed by the incessant flow of desires - can alone achieve peace, and not the man who runs after these desires & strives to satisfy such desires."