What stakes are you playing as well as game type. Game type probably has the biggest significance in what type of loosing streak is normal. Say turbo SNGs or MTTs will have a much longer and higher losing streak that is normal.

Something like cash games has a much smaller one as long as you are a decent player.
How long of a streak are you talking about. If it is short just play through it concentrating on playing your A GAME. If it is a long streak maybe it is time to think about your strategy.