In all fairness, you shouldn't entirely give into ANYTHING. I mean, there's just as much risk putting your faith in something new as there is in nostalgia, because both require you to invest interest into something to the point where you have a certain expectation to how that thing will be like. You don't just go into a new game blind. There's usually a reason why you WANT to buy a new game. Either you see the commercial/trailer and it interests you, year read about it in previews and reviews and you get turned on to the experience, but anyway you look at it, there HAS to be some interest and investment to catch you enough that you are willing to shell over the movie to buy it. The chances that the game will live up to your expectations or not depends on YOUR experience when playing it, but still, prior, your faith in it is nothing more than just that. Everything you see and read could be giving you signals that it's going to be an epic game, and then you play it and it's a let down.
Generally, I say "Oh well." to this sort of situation(regarding expectations and disappointment). There's an unhealthy kind of "padding" you see nowadays where people try to condition others to avoid disappointment. Why? Disappointment is a part of life. You going to be disappointed regardless. Something in your life will disappoint you, and your goal is to rise above it and carry on. I hate the whole, "keep your expectations in check/if you don't care too deeply, you can't be hurt" kind of mentality. If anything, it's just as bad as people who put TOO much faith and expectation into something(though if they are still able to rebound after disappointment, you can have as much expectation as you want). It's basically like saying, "Kill your emotions, and you'll never feel sadness!". It's the cheapo way out. No, feel free to expression your expectations and in every account you are let down, don't let disappointment keep you down, but get up and keep on going.
I also find the whole "nostalgia's a bad thing" as being tiresome. If you only live in the past, it IS bad, but the same can be said for those who ONLY live in the moment(the present) or only live on dreams(the future). If you only live in the past, you are blind to what's going on around you now and the future. If you only live in the present, you ignore the value of the past and have no tomorrow. If you live in the future, you are so caught up with "what could be", you don't take the measures of making that possible in the here and now. You have to be a person that exists in three periods(always acknowledging the past and it's value, making smart choices in the present and never stopping to think about what the future holds), which I think a LOT of us are.