off the top of my head...
* is the serve strong? is it going to the weaker wing? is it generally challenging the returner? if it's not, its easier for returner to dip it, drive it hard, etc...
* on contact, are you split stepping (or are you generally hopping on your toes - watch bryan bros)? if i were to bet, this is your problem
* interesting that you're mentioning getting passed down the line at all... to me, if i'm not getting passed at least once per game, i'm not being aggressive enough
* are you really watching the racquet of the opponent?
* when you do make a move, are you committing, or waiting to see where it goes first, then move
* what kind of ball is the opponent receiving where you're going... if at the feet of opponent, that's agreen light for me... i'm more cautious if it's in the fh strizezone of the opponent
what's your strat?
i never expect to win the point on a volley... like from the baseline, it's a boa constrictor of pressure where i'm maneuvering my opponents out of balance with each shot... occasionally i'll hit a winner, but not due to amazing shot making, but because i maneuvered my opoonent so out of position/balance that a "rally" volley becomes a winner.
in general, i don't think you can be too aggressive at net (eg. moving, poaching, attacking the middle), but you can be too aggressive with your shot selection/overhitting/etc...