When we are close to someone, our friend is a loving comparison we can use to know ourselves better. They connect to and affirm things we like about ourselves, they assure us we are worthy of love and of having our needs fulfilled, they help us open our hearts to appreciation of life, and having friends is as necessary to us as food and water.
Including the essentials of life, friends are the most important things we can have. Having friends has been what sustains us as a species. Friendship has more import on our mental health and happiness than anything else. Good friends provide comfort in stressful times, build and share happiness in good times, and prevent loneliness and isolation. They effect our mental health so much that the effects flow over into our physical health. The happier we are with our friendship group, the healthier we are and the more longevity we have.
So, if you can consider yourself a good friend, remember you are a part of the backbone of humanity, a shining hero to someone, and doing good.