If Allah has written for you happiness, no one can steal that from you, and if He has written for your heart to break, then no-one can mend it but He, so always put your trust in Allah.
Genuine happiness consists in those spiritual qualities of love, compassion, patience, tolerance and forgiveness and so on. For it is these which provide both for our happiness and others happiness.
Someone was hurt before you, wronged before you, hungry before you, frightened before you, beaten before you, humiliated before you, raped before you... yet, someone survived... You can do anything you choose to do.
The most venerable, clearly understood, enlightened, and reliable constant in the world is not only that we want to be happy, but that we want only to be so. Our very nature requires it of us.
From the greatest to the smallest, happiness and usefulness are largely found in the same soul, and the joy of life is won in its deepest and truest sense only by those who have not shirked life's burdens.