The term "happiness" is generally understood as the fulfillment of one's desires. Of course, what you may desire compared to what you may need at any particular time or place is not necessarily the same thing.
We need to recognize that all of our desires arise within our minds. We can't expect other people or things to make us happy. Only we can do that by the expectations, assumptions, and preconceptions we allow to guide us.
Desires may be initiated by any of our five senses, such as "I am hungry," "I am thirsty, or "I just have to have that item I see in an advertisement." Or, desires may arise in our mind when we compare ourselves to others, such as wanting a more expensive car than our neighbor has, to show others that we are more successful than our neighbor. Desires can arise also from using our imagination or projecting our lives into the future, such as wanting to be wealthy, powerful, or adored.
We believe that if we get what we desire, we will be happy. Conversely, if we don't get what we desire, we will experience unhappiness. This is especially troublesome when one's desires are not realistic or are beyond their capabilities or means to attain them. Experience teaches us that even if we obtain what we desire, many times our happiness is short-lived, only to be fueled by a new or greater desire. If, as St. Augustine believed, our ultimate desire is for God ("Thou hast made us for thyself, O Lord, and our heart is restless until it finds its rest in thee"), then no finite object or person can ever fully satisfy that desire. Only God's grace can.
Thoughts and emotions can arise within our minds at any time. It is ordinarily within our freedom to choose which desires and emotions we want to attach ourselves to or, instead, to just let them pass by like a cloud in the sky. Admittedly, sometimes this may be beyond your control, such as when you have an addiction, or a physical or mental impairment. Under those circumstances you need the help of God's grace, a "higher power," or some medical, psychological, spiritual, or other form of intervention.
Take some time to reflect on what you actually need, compared to what you desire. How are the desires you have chosen to pursue important in your life? What or who is driving your desires? Is it your ego? Is it seeking to meet the expectations of others? Are you comparing yourself to others? Are your desires realistic and within your capabilities? How do you feel when you don't get what you want? How did you feel when one of your desires was initially satisfied? How did you feel a few hours, days, or weeks later? What can you do to release yourself from your attachments to any excessive or unrealistic desires? Who can you rely on to help you?