What's the role of mother-day in regard of a blessed life?
I would like to paraphrase Luang Por Viradhammo, who cared for about 10 years for his elderly mother, in saying that it is good to have formal ways of bringing up and maintaining gratitude for ones mother lest we become complacent and let the importance they have in our being here fade from our minds.

With that in mind, I would say that exactly how you would internally use the formal occasion of mother's day is something only yourself can piece together. I hope the two links I am sharing can help give you a good starting point for reflection.

Dhamma talk by Luang Por Sumedho about gratitude to parents

Article by Ajahn Amaro