You have already chosen to place quiet prayer time and daily mass at the top of your priority list for the day. You have two choices, you can bump prayer time and/or daily mass, or you can improve your discipline and sense of urgency enough to make exercise a priority later in the day. I'm not a regular reader here, but I am a Catholic, and while I think daily mass is fine and good, I question why a mother of small children would feel compelled to attend. It is not required. Daily exercise, however, is necessary for basic health and maintenance of your body. Failing to exercise WILL shorten your life and put you at risk for serious illness such as cancer, which prevents you from serving God in the way that He intends. It is for this reason that we must take care of ourselves first, before others.
The anonymous commenter makes some good points. It is true that exercise is necessary to maintaining good health. I know I feel better when I exercise, that is why I struggle to figure out how to fit it into my daily routine. I also know that eating right is necessary to keeping your body healthy. Eating a lot of processed foods and not enough of the "good stuff" can certainly lead to serious illnesses.
I still maintain, however, that daily Mass is also very necessary for me in order to effectively do the Will of God in my life. I feel a very strong call to daily Mass and I know the many ways in which it benefits me and my family. I also know that my morning prayer routine is crucial for me to keep on track with the resolutions that I have set. Both the prayer time and Mass make it much easier for me to remain at peace. Fortunately I do have older kids which makes it easier to get to daily Mass.
That all being said, I think I like the way the commenter puts it, "...or you can improve your discipline and sense of urgency enough to make exercise a priority later in the day." This is the route that I have been trying to take recently. We have decided, for now, to take a walk every day after Mass as our exercise. We go to different churches ever day so it provides us with some variety. Each day, weather permitting, we get the cart out of the car, pop the two smaller kids into it, put on our gym shoes and start walking. So far it has been working out.
In this whole process, I've realized two important things. The first is that I have to place all of this in the hands of the Lord. I want to get in shape. I think He is calling me to get in shape. Therefore, I try to ask Him everyday for the grace to stick with a plan. The second thing I realized is that I have to take it one step at a time :) My personality is such that I like to dive into things full force and I expect immediate results. I have to come to terms with the fact that this might not be the best exercise plan out there for me, but for now it is what I can do - and it is more than I was doing before! Hopefully over the summer months I can add more exercising options in so that, come fall, keeping the exercise routine in my day won't be a big deal.
I'm glad for this comment since it got me to think about my priorities. I believe that both my prayer/Mass time and exercise need to be important parts of my day so I guess it comes down to discipline! UGH!