How fast am I, really.?

I have been thinking lately, how fast am I, really. How far can I push myself? Can I run a 7min pace and maintain it for a 5K? Could I run a 6min pace and would that be as fast as I could go? How long can I really maintain any given pace? Can I do it for a full marathon distance, 50K, 100M? Does the weather, temperature, humidity, and time of day affect my body's peak performance capabilities.I am sure that the summer is not optimum for performance testing, but when else am I going to get to test how well will my body perform under stresses that I can't control. I have to know how far my body is willing to go and when my mind will decide to turn it off.  It is always the mind that quits before the body. Will I be able to master full control over both and achieve what I now think is not possible.  Sure anybody can PR in optimum conditions, and complete control over most aspects of everything. I want to know that any day, any race, and conditions I will be able to PR, or match my best with no excuses. There should be no condition, no terrain, no equipment, no excuses for a poor performance. I want to be able to have my performance speak to the fact that I've done my best no matter what endurance competition I choose to enter. Sure there will be times that I didn't put up the numbers that I think I should have put up, but at least it should have been my best. Won't you join me on this new journey I have chosen. I will be updating the progress weekly here.