My Avatar has a lot of very deep personal meaning to me, as I'm sure everyone's does. I'll share what the symbol is, and some of it's personal meaning.
It's one of the 8 auspicious symbols of Buddhism, called the "endless knot." A lot of people think it's a Celtic knot, but it's very different. It represents the intense interplay of opposing forces which ultimately results in their union/connection, and ultimately their harmony. The fact that the knot has no beginning and no end suggests harmony and ultimate wisdom.
So... the personal meaning. There have been many times in my life where I have felt these strong opposing forces at play. Either me against another, or even watching from a distance two forces against each other. Some of these events have resulted in a great deal of pain and sorrow at the time, leaving scars. Ultimately, I see these events affecting my life as a whole, and they become a part of me, my identity. I'm not saying that all of them end up pretty, or that I find happiness from them. But, I strive to accept the truth and acknowledge my whole self.
As an example... I was married once (yes surprise surprise). After just a year of marriage my wife was pregnant with our baby when she, and the baby were broadsided by a drunk driver. She was placed in the hospital, lost, with severe trauma pretty much everywhere, lost the baby. I ultimately had to make a decision to keep her alive on life support although practically brain dead, or withdraw support and let her move on. I let her move on. Two opposing forces that stuck with me for a very long time, and over the years I have watched these forces come closer and closer together and knot around each other, weaving themselves as integral parts of my life. I can't say they are in harmony or at peace with my life yet, but I see it happening, and eventually it will.
I try to take that approach with all opposing forces in my life. Some of them unite and integrate into my life rather soon. Others, such as this case, take years, decades... perhaps a lifetime.