I remember reading a really poignant story and it has stuck with me forever. I would like to share it but I do apologise for not being able to reference it.
It was about a child, James, I will call him, feeling unloved and so very lonely. He felt like he was living a ghostly life, where no one noticed if he was even there. One day he was walking home, with his bag full and some children knocked into him and his bag fell off, with everything inside falling on to the pavement. They obviously didn't stop, but after a moment there was a boy crouching next to him. He gave him a big smile and offered to help. They discovered they lived near each other so walked the rest of the way home together. Just as they were about to go their separate ways they planned to meet in the morning and walk to school together again. This arrangement happened every day for the rest of their school lives and they are still friends now.
James recently told his best friend that he had saved his life and hadn't even realised it. He told him that the day they had first met, he had planned to take his own life. Had he not been shown such kindness, and someone wanting to be with him and liking him for being him, he wouldn't have been here today.
You never know what is going on in other people's lives and so have the courage to smile at someone, say hello or offer to help when someone is struggling. You don't know what a difference it could make.