You will never properly appreciate your own mother until you become a mother yourself. Which I realize is impossible for the (very few) men in the group reading this, so you'll just have to employ your imaginations.
But for the women, if you become a mother yourself, no imagination is required to realize how hard your own mother worked for you all your life, with very little recognition or thanks from her children. How she will always be working for you, albeit from afar and in a much different way, for the rest of her life. Because moms do that. You can't turn off the mom thing. Once that kid has arrived, you're a mom forever.
My own mother had three children within four years. We were a military family, which meant that especially when my siblings and I were very small, we moved a lot. Packing up three kids and moving them every three years (or even every year or six months, depending on the assignments) requires a level of patience, courage, and fortitude that I'm not sure I possess myself. To say nothing of the solo parenting while my dad was away for extended overseas training.
I have a good mother. A great mother, even. And now that I'm a mother myself, I realize how incredibly lucky I am to be given that role model for my own parenting.
So, to my own mother (who sent ME a card this year, and I didn't even send her one, which tells you a lot about her): The happiest of Mother's Days and all my love and appreciation. Thank you.