The word "miss" is also part of the word "love". So, when someone says, "I miss you!" it also means that they love you! Now, why did I text you? Simply because... I miss u
Somewhere, someone dreams of your smile and finds your presence in life so worth while. So when you are lonely, remember it's true that someone, somewhere, is thinking of you.
The essential sadness is to go through life without loving. But it would be almost equally sad to leave this world without ever telling those you love.