I can totally relate, my two boys are 10 and 13 and trust me when I tell you that you will miss those years when your kids were younger. It doesn't get any easier, well some things do but then new stuff that is equally tough and sometimes worse comes along.
Now that my kids are older I sometimes feel lost, when they were young it was all so much more simple, wholesome, even when I was exhausted. Just playing with them, rough housing and what not it was almost a stress relief at the end of the day to come home to my little guys and they were so excited to see me. There is still some of that but a lot of it just starts to feel like I am their manager and they are assh0le employees.
In the end though I don't know that I would change it. Sure, without kids I could travel more, have lots of leisure time and more time to train etc... But I just know how satisfying or rewarding my life would be without my family.