If you stop and think about this for a second it's really amazing. When we hold our head high, we are trying to raise ourselves above the mundane earth below our feet. We are trying to imply that we are closer to the heavens.
Generally we associate our sense of self as eminating from our head, because that is the vantage point from which we see and hear, but in actuality it makes no real difference which part of our body is the seat of the self--it's all connected, it's all us.
Our feet are right there, firmly planted on the ground at all times. Think about our feet as being us. Think about the fiction that are feet are not us, but that are head is. We are right there all the time, pressed up close against the ground. When we want to deny it, we raise our head a little higher, trying to hide our nature.
The amazing part is that towards the end of the Tanya, in Iggeret HaKodesh, Rebbe Shneur Zalman of Liadi brings down that the the ground, the naked earth, has the greatest revellation of Godliness in this world. It is the only place where HaShem's words can be seen actively involved in creating something from nothing all the time. (Everytime a tiny seed disintegrates and grows into a huge tree)
Sometimes, if we stop trying to escape and hide our nature, we can be so much closer to HaShem's Holy revellation. We can be flush with the earth (and HaShem's light therein) that forever supports us.
We can let go of the weight of being, and let HaShem carry the load for us--which He does anyway, but isn't it so much lighter when we know we aren't the ones carrying it?