Part 1
Hey, I have fangs ?!? I'm going to start with some elements that are common to all vampires. First off, you died. Dead. Life flashed before your eyes, light-at-the-end-of-the tunnel kind of thing. No matter who you were or how strong willed you are, the very first thing that happens to you is that someone faster stronger and nastier stuck his teeth in your neck, and drank your blood until you DIED.

That is not a good way to start out the rest of your existence. Then, just when you're getting used to this whole dead thing, as your soul is leaving your body, and you're pretty much resigned to heading off to your eternal reward, some nasty ass bastard comes along and yanks you back. Unh-uh, no afterlife for you, buddy. You're going to spend the rest of your existence right here, in this body. This DEAD body. That's right, dead. Your body is dead. The only thing that keeps it moving is the poor bastard stuck in it. Namely you. This is an experience to cause problems in the most stable personalities. How's your night so far?

Which brings me to the second point. Night. So tell me, what's it like never having any choice regarding when you'll sleep? As soon as the sun edges the horizon, boom, out like a light. You don't know what hit you and you stay like that until the sun is down. Oh, sure, if you really exert yourself, you might stay up for 10 or 15 minutes, but it leaves you drained for at least the next week. And what's the point really, you're groggy and can't make a coherent thought if your life depends on it, and oh yeah, don't get caught in that sun beam...can you say FOOM? Vampires are slightly more combustible than lighter fluid. And harder to put out too. Something to do with drying out and not decomposing.

And there's one or two other things too. Have you ever been hungry? I mean really hungry? Like haven't eaten in the last two days. Nothing at all? Then you know how hungry a vampire is right after feeding. Now, have you ever been starving? I mean literally, dying from lack of nutrition starving? I think you get my point.

Do you believe in God? In Hell? Eternal salvation and damnation? Because your character does. Or should. Because in Vampire the Masquerade, God exists, cursed Cain and all his progeny to eternal damnation. And somewhere deep down in your characters soul, he knows it. And then there's that whole Beast thing. You have this growling, out of control monster in the back of your brain, that can only process information in one of three ways; eat it, kill it, or run from it. And the really neat thing is that the older you get, the stronger it gets, until eventually you go stark raving mad and get put down like a rabid dog. Wow, eternity's just rockin' so far eh?

Part 2:
I Remember the Good Old Days Have you ever noticed that in any group of people mostly 30 or older, the conversation will eventually move towards "I remember when...", reminiscing about the good old days, and how much better things used to be? Well, I don't think I have to remind you that the average vampire is between 50 and 300 years old, with some oddball ones being a whole lot older.
So, Vampire the Masquerade being what it is, you've got an eternity of looking forward to things progressively getting worse. (until, of course, Gehenna, but we won't talk about that yet). And that's not even the best part!
Ok. Nobody is so utterly reprehensible that they don't have any friends. So you get to look forward to any 'safe' friends ( you can never trust another vampire, but we'll get to that later, too), family, kids, great-great-grand kids, anyone you ever meet, growing old and dying. Now some people don't have too much of a problem with that, they're expecting that, they steel themselves for that, but then they turn around and get floored by the fact that their favorite band is doing a comeback tour, and some of them are over 50 years old! And you still look 23.

You cannot prepare yourself for the world moving on without you. Your mind is built to grow old with the world around it, and keeps getting clotheslined every time it notices the world moving on without it. Because, and here's the real slap in the face, you're dead, and just too active to realize it. People and times will change, but you won't! Get it? No matter how up to date you keep yourself, or how fast a learner you are, you are still the person you were when you died, and will stay that person for the remainder of your unnatural life. Basically, you stop evolving and growing, and start reacting.