Guilt that kills......

It's Friday, it's mid August. the summer is going by so fast and I feel like I need to do more but I am not motivated. I feel like I wasted my summer. Maybe because I am working full time and I have 3 little ones at home. Life is hectic and I am scared that one day I will look back and regret this wasted summer. I try to do my best on the weekends but there is lots of earns that needs to be done for the week. I feel bad that the kids are not having as much fun as they should. Even though they are in a camp that has all the activities that they love but as a family we didn't do much. My husband travels a lot more now so this also makes it even harder for me to get everything done and entertain the kids to make their summer memorable. Sometimes when I think of things to do with the kids, I change my mind because I am to tired to do anything. Is that normal? every weekend I have all the intentions that I am going to do so much with the kids but life kicks in and makes it impossible and if I have some time I am just to tired to do anything. The guilt is killing me. Sometimes I feel bad that I went back to work after my twins started school. Because when I was home with them I was always there for them, we use to play more, spend more time with each other but not anymore. Is it normal to feel this bad? every time I read a quote that says "enjoy every minuet with your kids because you will never get this moment back" It kills me!! Life goes by so fast. At the same time I want to do something for me as well. from the moment I had my first till the moment my youngest started school, I dedicated my life for them. I wanted to be there for all their firsts and I was. I think it's time to have some me time but why do I feel so guilty about it?....