If we mistreat other people there is always someone who knows we did it and that is ourselves and generally this interferes with our self esteem and our happiness. In fact often bad behavior leads to self hate. Self love is an essential part of the joy of living, and so self hate from doing bad deeds takes that away.
There are people whose self esteem actually increases when they do something bad. They feel pride that they were able to get away with it. This gives them a feeling of power. I can't see these people as being happy though. If we mistreat others they are likely to retaliate and make us unhappy in that way. If we decide to spread sunshine in other people's lives we will bring happiness to our own. We may not always be appreciated by the other person but in general we will be. We have all benefited from the goodness of others and we all benefit by being good to others. Here are some stanzas from one of my favorite songs about goodness.
Angels Among Us
I was walking home from school on a cold winter day.Chorus
Oh I believe there are angels among us.
Sent down to us from somewhere up above.
They come to you and me in our darkest hours.
To show us how to live, to teach us how to give.
To guide us with a light of love.
When life held troubled times, and
had me down on my knees.
There's always been someone there to come along and comfort me.
A kind word from a stranger, to lend a helping hand.
A phone call from a friend, just to say I understand.
And ain't it kind of funny that at the dark end of the road.
Someone lights the way with just a single ray of hope.
Chorus
Oh I believe there are angels among us.
Sent down to us from somewhere up above.
They come to you and me in our darkest hours.
To show us how to live, to teach us how to give.
To guide us with a light of love.
Angels Among Us was written By : Becky Hobbs and Don Godman and popularized by Alabama