Is South Korea safe from North Korea?

I'm sorry, but I must ask: is South Korea really safe from North Korea? I've heard so much about the tense relationship between the two countries, and it worries me. With the nuclear weapons program and the constant military tensions, it seems like a powder keg ready to explode. Is there any truth to these concerns, or am I overreacting? What measures are being taken to ensure the safety of South Korea and its citizens? I'm just looking for some reassurance that my family and I would be safe if we were to visit or live in South Korea.