Why do I let him get under my skin?????

It just bothers me so much that I let his stupidity get under my skin. This morning I heard his oh so familiar ring on my cell phone so I of course ignored it and let it go to voice mail. Then he tried the home phone again no response from me. So then he sends me a text message just telling he wanted to talk to Austin to let him know that he was taking him to the driving range and the movies on Sunday. I responded by saying " How nice for you that you have money to take him to all these places and I have $6.00 left in my account until the 18th when I get paid again. I have no milk, no bread, or no dog food because I had to pay the rest of the $700.00 electric bill he stuck me with when he left. Not to mention all the other crap I have been struggling to pay on my little paycheck but we are doing it the kids and I. I just told him how nice for you that you have money for all these fun things when i'm just keeping food on the table and gas in the car to get us to school and work. Then I tolld him I would have Austin ready for his one fun day a week with Dad then make sure he had him home by 6:00 for Sunday dinner with me so I could do all the important stuff that will matter in his life. Guess he didn't like that because my phone has stopped ringing..... What gets me is how I let his stupid mouth and stupid choices still bother me. I need to get a thicker skin when it comes to him and I have to keep telling myself he is a selfish, self centered, i'm going to do what feels good to me no matter what who it hurts or effects. So it really shouldn't suprise me that instead of giving me money to buy food for us he is going golfing and to the movies. And what kind of mom would I be if I denied Austin this one fun day a week with his dad. I just have to let him go and hope that in a few years from now Austin will realize who really took care of him and who was the stable parent in his life. Oh I hope this feeling of being upset when he says and does stupid things will pass some day.