If I recall correctly, this is something that Tyrion says to Jon Snow about being a bastard. Tyrion is saying that other people will be aware that Jon was born out of wedlock and that this fact will influence how they treat him (specifically, they will treat him more poorly).
Tyrion's advice is to not bother trying to hide that fact or to pretend that it isn't true, since other people won't cooperate with those efforts. Instead, Tyrion suggests that Jon embrace it. If Jon never pretends to be legitimately born to Ned, no one can hurt him by revealing the truth. If Jon accepts the conditions of his birth as a part of his identity, no one can hurt him by reminding him of something he's trying to ignore.
Opinions can differ on the deeper meaning of the quote, but my read of it is that other people will try to hurt him in various ways due to his illegitimate birth, but they won't succeed if Jon always remembers and is true to who he is.