I struggled with the balance between "pride" and "self-esteem" for years, until I actually read what the apostle Paul said: "Let no man think more highly of himself THAN HE OUGHT TO THINK, but in lowliness of mind, let each esteem other better than himself."
There is absolutely nothing wrong with being confident in who you are, and who God has called you to be. The secret is to not allow that confidence to become disproportionate, for then it becomes pride. Consider those around you to be your equal—even better than yourself (that will certainly keep you from elevating "self" too highly)—but never, ever sell yourself short, or rob God of the value He has placed on you.
Low self-esteem is the result of not having a complete understanding of how God sees you. When God looks at you, He doesn't see a "loser", or someone who's too short, too tall, too thin, too fat, someone who wears glasses (my own Achilles' heel when it comes to self-esteem), or has freckles, a double-chin, a big nose, big ears, etc.
In short, God does not see you as a loser, a failure, inept, awkward, or out of place!
When God looks at you, you know what He sees? He sees His creation: the work of His own Hands. He looks at you and thinks, "That is a work that I designed, that I created; I breathed life into them. They carry a part of me in them; they have my DNA. That is MY creation!"
Be honest: have you ever seen a newborn that was just...well...homely? They're not the prettiest things to look at, but you'd never convince the parents; that is their offspring, a part of them, something THEY created, and they're as proud as ever a person can be when they show that baby off to the rest of the world. You're a child of God—YOU ARE HIS DESIGN!—and He is only too proud to look at you and call you His Own Design.
Walk with your head up today, not because you're "just that good", but because you recognize that you are a product of God's own Hands, His own breath, and He is proud of His Creation when He looks at you!