I am an old school roleplayer, and i have to admit that if there is one thing i have hard time to accept, is this kind of players that don’t care about their character, shouting proudly in the middle of the deadly encounter “Oh that’s ok, i can rebuild a character if needed !”
Sorry but no. I truly think that your should play your PC in game almost like your life IRL was depending on it, feel the adrenaline of a bad fight, the fear of seeing the death of your alter ego, amongst the rest of the group also trying to survive and probably not able to save you at the moment.
RPG like D&D offers lots of backup possibilities, spell of healing, resuscitation and even resurrection could bring you back to life with your full hit points at best. But i think some players tend to see their characters as consumable and i cannot get along with that.
When i started D&D 3.0, i was a Cleric, and it was my first character ever, i care about it so much i played it very carefully and had several times some cold sweats during fights. Fear of not using the proper spell, fear of getting hit by an opportunity attack, and worst, going down while i was the only healer, big pressure !
But at no time, i ever thought to replace my alter ego with a character almost pulled out of my hat, expressing no remorse for my maybe dead cleric ! No, i wanted to fight for him, to think smart for him and to evolve in order to become better.
I heard someone saying one day that in each RPG character, there is a part of you, weither it is the way it reacts in a certain situation or the way it fights or deals with socializing. Sometimes it reveals your true nature if you were not framed by our culture limitations, and clearly reveals some fantasy as well haha.
Your PC is important, because it is you.
Another aspect is the respect of the GM. Not playing your character seriously is disrespectful for the person that had pulled all this great scenario for you guys. Writing a script, bringing cliffhangers, giving some turning points, massive surprises, betrayal to make you clearly live as your PC would, plunging you in his movie like a director on an audience in a theater that would identify themselves with heroes of a movie.