I suppose it's different for everyone, but for me, it was beyond fucking terrifying. I don't even know how to explain it.
It's a long story so I'll try to keep it short as possible, but about a month after my 19th birthday, I got robbed (at gunpoint) in my own house. Someone knocked at the front door, my dad opened it because they "looked familiar" and I didn't really think anything of it until I heard them bickering.
The guy was asking for someone who didn't live at our address. My dad insisted no one by that name lived here, but the guy at the door didn't believe him and made an argument about it. So I got curious, stood up, went into the hallway (which isn't too far from the front door) and peeked out to get a look at what was going on. Bad move on my end. The guy sees me, gets the idea that more people are inside, pushes past my dad (who, for some reason, didn't fucking react at ALL) and pulls a revolver out. It was pretty small, silver-ish in color. That was my first time seeing a gun up close/in person, so when he pointed it at my dad, I freaked the fuck out and ran to my room, not knowing what to do. I remember closing the door and looking around, but my mind was blank for a few seconds. Never understood the whole "mind goes blank" concept but it happened to me, I literally didn't know what to think, which resulted in me blankly looking around at the walls for a bit. Finally, I snap back to earth and I get to thinking like: what should I do? I knew I couldn't fight him. I was tiny as hell compared to him, and defenseless against his gun. I looked towards my phone, which was lying on my bed, but figured I couldn't call the police because he was RIGHT down the hallway and if he caught me, he was going to shoot me. So I threw my phone under the mattress. Right when I did that, he's screaming for me to come out of my room and I oblige. I open the door and walk slowly with my hands up towards where he is. My dad is on the floor, and the guy points the fucking gun at me and demands that I get on the floor next. This was a huge inconvenience for me because I'm a girl and, you know, monthly girly issues - but I did it, anyway. I just kinda laid there, half listening, half praying. I'm not religious at all but I just kept whispering to myself "God please don't let him kill me" over and over again. The next few minutes after that are kind of a blur, but I remember at one point, he made me sit up, then he positioned himself behind me, pointing his gun at the back of my head while he ripped my necklace from around my neck. At another point, he discovered that my dad lied about not having money in his wallet, so he pointed the gun directly at my dad's forehead and put his finger on the trigger. I begged him to not shoot. That's another terrifying concept. Watching someone you love and care about have a gun pointed at them. Anyway, the dickhead pointed the gun at me again (briefly this time) and told me to shut the fuck up, then went back to arguing with my dad. Then, at ANOTHER point, he was screaming at us to comply and opened the gun up really quickly so we could see that it was loaded. Within that whole fifteen minute ordeal, I really did think I was going to die. I mean, he wasn't covering his face at all. No gloves to mask his fingerprints. To me, that translated to: I'm not hiding who I am, so I have to shoot you so you can't identify me later. And I think that was the most terrifying thing in itself. Feeling like I was going to die then and there - especially in such unfortunate circumstances, being so young, not having accomplished anything that I wanted. I thought about all the people I hadn't spoken to, what I wish I would've said to some of them (like my mom, for example) and I thought about what they would think, how they would find out.
Things ended on a semi-good note, at least. He left with some of my stuff, but I lived to tell the tale and no one was physically hurt. My dad was alright afterwards, he said it wasn't his first time going through such an experience, but that was clearly a first for me and it left me pretty shaken up. To this day, I have nightmares all the fucking time involving guns and every little noise I hear after midnight makes me panic, I literally sleep with a knife and a machete near by. But as far as the whole "appreciating life more" deal goes, that never happened to me.
Anyway, yeah. Horrible experience. Hope I never have to go through something like that ever again.