Humility is a tough thing to talk about because if you talk about it, people think you think you have it. And humility is one of those things, where if you tell people you have it, you don't have it at all. So, let's get this straight: I'm a prideful, arrogant, self-serving windbag who doesn't have humility, but is going to tell you all about it. 

Humility (contrary to popular opinion) doesn't mean "believing only bad things about yourself." It means "having the same view of yourself that God has of you." That means, we are wicked and evil and incapable of doing anything on our own, but that we're also someone for whom Jesus Christ saw fit to die (1 John 2:2), someone Jesus has gifted extraordinarilty (1 Corinthians 12:7), and someone through whom Jesus Christ promises to work (Philippians 4:13). You can have an extremely high view or extremely low view of yourself and be prideful.  

As a result, humility has to be born out of a knowledge of God as much as it is out of a knowledge of ourselves. If we don't understand who God is, we can't understand who we are in relation to Him. And if our humility isn't born out of a knowledge of God, it will be self-focused and fake. In fact, it will just be one more tool we use to beat others over the head with how much better we are than them. 

Finally, humility is never self-focused, but it is always others-focused (John 13) and God focused (Luke 18:9-14). If you want to know whether or not you're humble, the question isn't whether or not you feel humble, but whether you approach God with due reverence, and other people with due dignity.