I talked the other day about preparing for Holy Communion in order to be receptive to grace, but cooperating with the grace that God is waiting to give to the soul in Holy Communion doesn't stop there. It is also important to be attentive during Mass. For me, at the moment, the best I can do is prepare, try, and realize that if I am distracted by meeting the needs of a wiggly baby then there is merit in that also.
That brings me to the practice of making a thanksgiving after Communion. If a beloved and awaited guest arrived at your house, would you say, "Hi. Sorry. I'm really busy today. I have to run. See you later!" and go on about your business? Certainly not! You would sit down, spend time with your guest, chat, catch up, offer a drink, etc. You would put aside other things and spend time with your guest. How much more then, should we put aside other affairs and spend a few minutes in prayer with our Lord after receiving Him in Holy Communion?
This is challenging for me for several reasons. When Mass ends, I still have the baby. Sometimes she has fallen asleep, but more often she is awake and, having reached the end of her attention span, needs something new to do or look at. Where we go to Mass there is also the commotion of people leaving the church, chatting (sometimes while still inside the church), and sometimes wanting to strike up a conversation with me (I am holding a baby, after all -- the ultimate conversation starter).
Because it is no longer necessary to be absolutely silent (the church is not silent anyway), I solve the problem of a fidgety little girl by talking to her. I simply include her in my conversation with our Lord. I explain what we're doing and pray with her. We make a simple act of Faith and adoration, thank our Lord for the privilege of assisting at Mass and coming to me in Holy Communion, and make whatever petitions seem appropriate. If, for whatever reason, this doesn't seem to be working, I go out of the church and wait for my husband to be ready to go, and then go back into the church for a few minutes while he entertains our little girl.
I think the effort to spend at least a little time in thanksgiving for Mass and Communion (incidentally, I would make a thanksgiving for Mass even if I didn't receive Communion) is more important than the form. It is fitting that it should take place immediately (after all, you wouldn't receive a guest into your house and then abandon him to his own devices for a couple hours without a very pressing reason). If your situation allows for such helps as holy cards and printed prayers, there is another excellent prayer by St. Thomas Aquinas that matches the one I suggested for preparation.