It is of utmost importance that we see our value, not in some prideful attitude of self achievement, but as helpless human sinners. Yet as sinners with value, our value is based not on what we are or can do, but because of whose we are!
In the same way that the price of an item goes up or down based on whose brand name is on it, you are infinitely valuable to God because you are made in His image (Genesis 1:27). When you accept Him as God and acknowledge your need for Him, you not only are saved, you become adopted into His family and are now considered His child. How cool is that?
It's so easy for us to forget how much we matter to God because so much of our world around us derives it's value from things like what you own, what you've accomplished, how many people know you, etc. But when it comes to your value, it is fixed and proven by what God was willing to give up for you to be reconciled to Him: His Son, Jesus.
Any time you feel lost, forgotten, unloved, or worthless, remember this. You are more known, cherished, adored, and loved than you could ever possibly imagine and no matter what happens in this life, you could never change God's mind about that (Numbers 23:19).
You matter. You are important. You are loved. Your presence on this Earth makes a difference whether you see it or not.