Don't be mindful, Be Prideful.
Although most of the time he didn't mind his tiny body, sometimes Pride would catch himself wishing that he could grow. Not too much, mind you, but just a little bit. He never liked that those who did not know who he truly was always looked down on him, thinking him nothing more than an incompetent child. How wrong they were.
He is his Father's favorite. Although he never says it, Pride knows it, and so do the rest of the Homunculi. It is an unspoken kind of favoritism, but it still carries weight when Pride must deal with his Family.
Pride has been there from the beginning, learning and growing along with the other Homunculi under his Father's careful tutelage. Although he is not human and therefore should have no human emotions, he gets this funny feeling in his chest when it concerns his siblings. Like when Greed betrayed them, he felt that he had lost a vital part of himself. Or when Lust died, he cried for the very first time.
Now though, he has gained a new brother, the newer version of Greed. Pride likes this version of Greed a lot more than the other one. This new Greed treats him with respect, but a respect that was not born from fear. Pride is filled with the sin he is named after when ever he looks at the younger siblings that he has taken under his wing over the years.
And as he watches his father sleep in his chair, Pride's face begins to change from the innocent expression he normally wears. A vicious sneer forms on his face as he contemplates what will happen to those little humans in the military when Father's plans are finally set in motion. He thinks of the many different ways that they could and will die.
And when his thoughts arrive on Riza Hawkeye, Pride wonders if Father will allow him a bit of pleasure before he breaks her neck.