My kid left...

I have two kids.  One from my previous marriage, who's 6 years old.  And the other from my soon-to-be husband, who's two years old.  My older son decided that he wanted to live with his father full time instead of spending most of his time with me.  We had to come to this decision because he started acting out, especially on his days with me.  He said my household had too many rules; we were too strict. His daddy and grandparents pretty much let him get away with murder.  His behavior caused a lot of arguments between me and my other half, and it wasn't fair to the little one.  He started acting very rough with his little brother, and that's when I said, "No more!"  The next day, his daddy picked him up and he hasn't been back since.  It's been over 2 weeks...
At first, of course, I was very sad.  Feeling like a failure as a mother because I expect my child to be a good kid.  But I realized even if I tried my best to try to teach him to make better decisions, he was going to make his own.  I can't control him.  He's very smart, and knows how to manipulate the hell out of his parents and grandparents.  So, no matter how we tried to discipline him or even cut him some slack, he just continued to get worse, especially in school.  So, I thought maybe it's just too much for him to go back and forth between two households.  I asked him who he preferred to live with, because he needs consistency.  That's when he decided his father.  And I knew he would.  His father is single, lives right across from his parents, and has no other kids.
I have so many mixed feelings.  But I knew this day would come...just not to soon.  I will continue to support him.  I love him no matter what.  This seems like the better decision for us all.  It was just getting to be such an unhealthy environment.  I want him to be happy, but I also want him to learn to do the right things and make good choices.  I just want the best for my kids.