Is it ever ok to be tigh-Agg./Passive?

[ChrisEuph]

I have played 5057 hands so far and use poker tracker. It has auto rated me as Tight-aggressive/Passive. I know that the best players are Tight and Aggressive. Is there any room to be as I am currently labeled? I play 1/2 limit and am starting to move up to 2/4. I wonder that for the time when you are in the low-limits w/4-6 players per flop, do you have to be aggressive when you miss the flop or have an underpair? The odds are there sometimes to make the call w/overcards, but never usually there to try and hit the miracle set. I am still a beginner and want to learn so any input is welcome. btw...I have read SSHE and am tring to apply the ideas of raising more w/less than top pair to provide free cards, etc...but am still new to applying them correctly. Thanks