It's something I feel strongly about, but it's hard for me to put into words. I'll try.
To me everything relies on integrity, which to me is defined as doing the right thing, for the right reasons, no matter who is watching, not watching, or what the consequences will be. Integrity = truth. Truth in a broad sense not just, "Oh it was me I did it," but internal truth almost akin to personal enlightenment. It's not always or often easy and it's both internal and external.
For example, you want to lose fat. Most people probably don't think about it, but you have to have integrity to do this. First you have to be honest with yourself, where you want to go, how to get there, your limitations, etc... You have to hold yourself to a certain standard, which relies even more on personal integrity.
Another example is living an honorable life. This one is easy. You can live like a gallant white knight saving damsels in distress all day/night long, but if you bed one of those damsels and your married, you have no honor. Cheating = breaking of vows = lying.
Everything in it's most basic form boils down to, "is it right," or, "is it wrong." If you live a life striving to be one integrity you will answer this question the right way, at least as best we very fallible creatures can.