We’re all charged by G-d to observe His mitzvahs, and our people have long followed that path. It’s just that some of us do it nonchalantly, by fulfilling their obligations to be sure by being here or there when that’s asked of them, and doing this and that when that’s what’s needed, but they do nothing more. No passion, no zeal, no search for G-d.
However laudable it is to observe the mitzvahs (and it’s quite admirable to make a life-long commitment to G-d Almighty day after day when the great preponderance of humanity turns its back on G-d), still and all one who follows through in that sort of casual way simply isn’t “pious”.
Only someone who not only fulfills his or her obligations to G-d but offers a gift to Him, if you will, in the process — who not only does what G-d requires but does mitzvahs as a sort of offering of sheer love to Him is truly pious.
As Ramchal words it, “one who truly loves G-d wouldn’t merely set out to do what all of Israel‘s obliged to do”. Instead, “he’d act like a loving child” by “doing even more than what his father would ask for”.
And so for example, even if “his father had asked for something only once, and demurely at that, that would be enough for such a child to perceive the extent of his father’s true wishes”. The loving child we’re asked to emulate “would deduce that such-and-such — something beyond what he was told — would actually make his father happy” and he’d set out to do it.
“One who truly loves G-d” and who’s thus fitting to be considered pious, “would have just this sort of reaction to Him”. The mitzvahs “would be mere allusions to him of G-d’s actual wishes” and he’d expand upon them.
Piety is also the obverse of abstention (our last trait). For where abstention came down to avoiding sin, piety is rooted in seeking out mitzvahs. But abstention and piety are actually two sides of the same coin in that both are rooted in “superseding the letter of the law … to bring satisfaction to G-d”.