Drabbles, because they are easy to do. The third unmentioned person, a 'she' can be anyone - I didn't have no one particular in mind.
...Happy...
Harry had never really known what it was like to be happy until he met his three friends. His mother and father had died at the hands of a dark wizard, his aunt and uncle treated him like a dog they simply didn't want but had no choice of taking care of him, he had to find his own way in the world, and even when he was content, he was never happy.
When she came along, she had showed him what it meant to be happy, to have friends, to be loved. He had heard somewhere that happiness led to love, and being in love made her truly happy.
He was truly happy.