The best advice I've received, and therefore can give, is somewhat religious but spans across more religion than one. Growing up when I would get angry or be mean to my little sister my dad would say to me " Imagine she's the baby Jesus, Jesus is everyone you meet." At the time I thought, "Pssh, yeah ok dad," but as I got older I started to hear this message reiterated in different ways. I remember distinctly hearing Robert Thurman, a famous Buddhist monk, and Uma Thurman's dad, speak about the teachings of Buddhism. I was beyond impressed with what he had to say, but one thing that I've never forgotten was something he said about their belief in reincarnation. He said that because they believe in reincarnation, everyone you pass on the street, could be your mother, or grandmother, or relative, and therefore you should acknowledge everyone you meet as if they were your mother in a previous life. I think of this as a similar teaching, because mother's are typically someone we hold very dear to us. He used the example of when we walk down the street, people tend to avert their eyes from one another, instead of looking and smiling, like you would (hopefully) if you saw your mother, the one who gave you life, walk by. Even to an extent the word "namaste"- the light in my soul acknowledges the light in yours, speaks to this idea of seeing everyone as if they are special, and important.
It can be very difficult to see Jesus, or the light in someones soul when they are cruel, or grumpy or hurtful to you. And it can be especially hard to see that person as your mother, but I think if you focus on the idea of treating each person with dignity and love and respect, no matter what- the world will become a better place. That is why this is the best advice I've received and can offer.