i also always have earplugs with me, or within grasp at my desk.
i have a choice of 4 types with me, depending on the situation
the ones i use the most are regular music player earbuds, the ones that let some sound in so i feel safe using them when cycling somewhere, and generally knowing what's happening (i rely on sound for most of my situational awareness).
secondly, i have noise-cancelling music player buds, which i use if the neibourghs have too loud music, or when in public transport.
aside from those, i got custom-made musician earplugs, they cancel almost all sound, but still let me hear voices, so i can still have a conversation or something when i'm in a bar or simular.
lastly, i got some of those foam industrial plugs which i wear if i want to sleep trough noise (i dont want to risk the custom plugs sleeping, they are too expencive for that)
however, even though i carry them at all times, i'm reluctant to use any that isn't the first type (regular mp3 buds), since they are uncomfortable in my ears, and i dont want to get too used to the lower sound, becouse that will only make me unable to live without them.
secondly, there is the problem that for about 10 minutes after i take out any antisound, my hearing is even better then normal, causing anxiety as well...