I love people who are apologetically themselves; it is so intoxicating to find someone who loves themselves the way they are. Just don't be pompous, and don't impose your confidence on others. Don't abuse self-confidence. I love confident people, but with certain limitations. People like this are hard to come by, especially in this society.
Comparison is the root of all evil. It grays our days and puts a damper on everything we could ever appreciate, where we achieve something great, someone somewhere has achieved something twice as great. Instantly, the notion that we've improved our-self vanishes, and is instead replaced by jealousy, saturated with a mentality of inadequacy.
If you aren't confident, find your confidence. Search high and low because I guarantee you that while you might exist secretly loving someone, there is someone out there secretly loving you.
Do not put your confidence in other people's hands. Who are they, but a passing stranger in your life?
What do you have to be insecure about? Everyone gets acne, we all just deal with it differently. All of your scars, stretch marks, bruises, freckles, birthmarks are nothing but paint marks on the blank canvas you were when you were born. They are nothing but fragments of evidence to demonstrate how much you've lived, how traveled and weathered you are. The sun has shone on you, and you've grown into something beautiful.
Brilliance is sexy. Knowing and caring about something is sexy. Being able to stand your ground on an argument is freaking fierce. Meaningful conversations and arguments are crucial; these build a character.
Be able to do things by yourself. You do not need a companion to accompany you to lunch. You can sit in silence by yourself, chewing thoughtfully and looking anywhere down but at your plate. You do not need a phone to scroll through, you don't need to make others think that you are busy, because when you sit by yourself and have the dignity to look around and be content with your situation, when you are justly humbled with that you gain a level of confidence that most of us do not get the opportunity to feel.