define yourself....or not....

My Guy told me last night that I should set realistic goals for myself and not worry about anything or anyone else.  This all stems from the fact that I am in no way shape or form ready to run the Chicago Marathon.  This was a realistic goal in March - but when you struggle with 6 miles - 9 weeks before the race -- it is not gonna happen.  I wanted to be able to say I ran a marathon in my life, but I let the training slip and I am struggling lately to be able to just push through it.  I underestimated the challenge.  My real goal at one points was that I wanted to do an Ironman.  Years ago I watched on TV some 80 year old woman finishing this Ironman in Hawaii and thought it was really cool she was so old and kicking ass.  I wanted to be that person.  I completely underestimated the level of commitment and challenge if would be for me.  I have not even gotten close to my first step in that goal - a triathlon - because I have not mastered my fear of swimming.  

What would be a realistic goal for me that is not just being a quitter and a loser? In this Precision Nutrition program I did they said that you need to define yourself as a healthy athletic person who eats well - so you would not feel you needed to cheat or where denying your self things your really wanted.  To really embrace your goals as your self definition and you then could achieve them.  If you have been paying any attention to this blog, you know I have no idea how to define myself.  I only think about what I do not do well, not what I want to be or where I want to go.  Often my goals are just vehicles to the self-flagulation of failure because I never believe deep down I can do it.   I look at my friends that have committed to these goals - hell even My Guy -- they train and the feel the pleasure of the success.  Why I am mentally blocked like this?   It has to be all mental - my body can not just suck more than everyone else's...so why am I so stuck?