My son just turned two last September, so he's at the stage of what they said as "terrible two", but I'd strongly disagree about that cos though he's causing me headache sometimes (I guess everyone, no matter what age can cause headache too, right?!), but he is always the best thing in my life.
Why two's not terrible?
I'm a living witness and I can definitely say that two's not terrible because now that my son is two...
...he is starting to be responsible -- he always remind us when to feed the cats, that he needs to take a bath, he needs to take his vitamins, etc;
...he is very helpful -- he'd feel bad when he can't help us doing the household chores, especially throwing out the trash and you can really see his happiness each time he's able to help, of course, we always make sure that we acknowledge his helpfulness and our appreciation;
...he has become more sweeter -- since he knows how to talk a little now, he has been really vocal about his feelings which makes him really affectionate, such as he tells us "i love you" as much as he can, then he'll kiss and hug us whenever he feels like doing so;
...he is learning right manners -- he's been really good about being polite, like saying "please" whenever he ask something, saying "thank you" if someone gave or did something to him, saying "excuse me" when he belched in public and when someone belched and forgot to say excuse me he'll say "excuse you"; and
...he is such an angel no matter how old he is as long as us, as parents, would continuously guide him of becoming a good person.
Those are just few reasons that I can think of right now why two's not terrible and I know there are more than that. And I can't believe why'd somebody would say that two's terrible 'cos I can never find any reason to say and believe that.