When you engage in the modest acts of kindness and generosity that are called good deeds, such as sharing a smile,
It is a joy when you have the opportunity to interact, share play and joke with a loved one because that is certainly what they need around them which is happiness. Many don't actually know the importance of people around them until they are gone which is why it is good to appreciate anyone that comes your way we never can tell what will happen tomorrow but we should always spread the word of love to others.
this reminds me of "Yesterday is history. Tomorrow is a mystery. Today is a gift. That's why it's called the present." Some say life is short, some say life is too long - well, it's precise, isn't it! A part of it spend on creating memories and the other part to reminisce those moments
This is one of my favorites. Simply said but the meaning is deeeeeeeeeeep yet simple to understand.
That is what mostly happens. I think the reason for that is lack of observation and yes appreciation as you have mentioned. Lack of observation may lead us to come up with conclusions that shouldn't be drawn.
I also agree with @surrealfia, indeed life isn't long and isn't a forever long ride. So, the many memories we create if we take a closer look at it, maybe we will create different conclusions. Sometimes, small actions matter the most.