To be honest, I felt this question too, and still do time to time, but if you look at how life cuts your pride down one side while strengthening your confidence in your ability to shape and mold your attitudes, humility is maintained by never avoiding the part that cuts you down to size...
So for example, the other day I felt great, because I accomplished this great bit of work for an important deadline, the next day I got completely crapped on by the same people who were so happy with me.
What should I feel? Proud of good work, crappy for all this blah side? Well, the truth is I think now, a few days later, this is the flow. This IS what keeps you humble. Not clinging to the "happiness" you experience by practicing dharma. That is, the happiness is just a state of ease, so no need to cling to the ease of feeling like you don't cling to the road that you travel...
When you feel boosted by the good, if you feel nervous about growing a seed of arrogance, accept the next time you are cut down size with good grace, that this is just another occurrence like that happiness.
I too feel happy most of the time now even when life is crappy, but sometimes I panic that I've got it "too good" now. But that's silly, all I've got that's good is a better mindset. My conditions aren't that much easier just because I'm ok with what I have to face every day. So while life is what it is, I am more of who I am in this tranquility I'm cultivating...
Remember the mindset is a tool, not the end goal of your practice. That should help you maintain humility, as you won't attach meanings to your tools that are more than the tools themselves. I see arrogance emerge in people when they forget that they also just poop and pee every day like any other living being. They get stomach aches, no matter how wise or unwise they are... LOL Rejection hurts, wounds cut, and hope and fear is experienced by all that is sentient.
You too, are no better or worse, and enjoy that happiness you experience, it's the fertile ground for your growth and development of your subtle mind... You too, are a buddha in the mire, just remember the mud is what made you, and you will keep a humble mind.
Mama's two cents worth...
I am beginning to feel my daily life improve as I think positive thoughts. Even on the cloudiest of all days, I feel..happy. Other than that, with my practiceof Dharma, I am beginning to feel internally happy..even bit by bit. I realize things little by little as I go on living my days.
The thing is, I dont want to develop arrogance. Im not really afraid of this though, but I just want to be aware of these feelings. I dont want to think or develop a mindset of "OH, Im soooo wise. This person knows nothing and is dumb".
I recognize that I am imperfect. I still have desires and attachments. Im a human being..just like anyone else. I dont like bragging or boasting about myself. When I am praise by others, I thank them for their kind thoughts but I say "no, I still have a long way to go". Whether it be with religious practice, calligraphy, music, art, or when people describe me as nice.
I've heard a saying the says "The more one knows, the more humble one is".
I want to be a simple person. How can I prevent arrogance from leaking
in and causing me trouble? Is this what Shakyamuni meant when he taught to guard your mind just as soldiers would guard carefuly a town to prevent bandits from entering? (okay, that was paraphrased