my first time my ps3 shuts down on its own

hey guys,

Thank you so much for the continuous help :D
the PS3 is a beast. I love it, with all this ps2 classics and ps1 classics and such.. but mostly PS3. Anyway, let me cut to the chase..

I'm playing my PS3 (PHAT) for like months now.. i played several games only on my external hard drive and I've been playing countless hours. THE ONLY problem i got with the ps3 shutting down was when I installed a PS2 classic of Playstation's 2 "SNK vs. Capcom2" which was awful!
this only happens to me on PS2 classics, damn that PSNstuff program. i knew it was kinda dodgy.

Anyway, Last night i was playing Ni No Kuni, I guess i did play for over 3 hours and then the ps3 shuts down on its own..this is the first time it happened to me on a ps3 game! (i've been playing this game for over 10+ hours into the game..plus several other games..first time happened to me). it just shows me the red blinks so i close it..Please tell me its fine. I know its the red ring of death or something or YLOD, but its my first time for me.. I don't think it will happen again..right? and if it did..what then? :(
I'm kinda in a panic..

and sorry for my bad english.. You guys are the best and I love this forum.