Relish your life. I know that it is hard at times. I know that sometimes it feels like this is all too much work, and it is never going to end. But the truth is that you are living the dream, and this will pass all too quickly.
Squeeze those chubby little baby legs. Kiss those beautifully soft cheeks. Listen to that beautiful gurgly laugh. Imprint that girl's stunning smile into the very depths of your memory.
One day they will be grown up, and it will all be gone. I know that it is hard being a Mummy all of the time. But cherish the fact that you can be a Mummy all of the time. Be grateful that you can belong to them exclusively. Be thankful that you have the freedom to enjoy this gift of childhood.
Even though you are so, incredibly tired and you feel like you are never going to get yourself back again.... remember that you will. One day your body will be yours again. One day they will no longer belong to you like this, and you will miss being their everything. One day they will have problems that you cannot fix with a kiss and a cuddle.
Remember that some people cannot have children. That they are desperate for the thing you take for granted. Remind yourself that what you have is precious.... and it can be lost. Hold on tight to those little hands. Glory in the wonder that is motherhood. Try not to yell, or scream, or lose your temper. This time is too short to be unhappy. But if you do... forgive yourself, and move on. Nobody is perfect, and what you are doing is very hard. It's okay to fail and struggle.
You don't have to enjoy every minute of it. Changing dirty nappies is not fun. Cleaning is not fun. Rocking and cuddling upset children when your eyes are hanging out of your head is not fun. Chasing a cheeky toddler down the aisles of Target while holding a grumpy baby is not fun. But enjoy the good moments. And remember that the bad ones will be over soon, even though it doesn't feel like it.
Above all else..... Love them. Love them extravagantly. And remember this. So much of this is fleeting, even though at times it doesn't feel like it. But you will never get it back. Don't waste it. Embrace it. Own it. Don't let yourself get in the way of the joy that is being their Mummy.