Improvise,adapt and overcome. -someone.
If you use a same strategy each time, ur opponent will catch it and counter accordingly and once they understand it they will overcome.
so the thing is to keep changing or modifying.i usually dont use the same stretagy twice a player.
There's nothing wrong with playing only one opening especiallly if it's not dubious or is not very sharp.For example I wouldnt advise to have a repertoire based solely on a Danish Gambit or King's Gambit.Because your opponents will either engine cook you to death or they will choose a sterilizing variation which they have more experience on and thus taking the fun out right in the opening stages.
The English is a very versatile opening and is based on ideas rather thn on concrete variations.It's a very good choice.Just tweak your variations.You don't necessarily need to switch openings because the English is very rich and ripe with ideas.
If your opponent can outplay you just from the information that you play the English, they are simply a better player. Nobody can prepare for all variations from the first move.
nice lecture by seirawan on strategic thinking in the opening, using the english opening as an example. (i realise this is only loosely related to the thread)
http://www.youtube.com/watch?v=Ohf79-nlekc
Thank you very much to all your replies..More Power!!!
As they said, if your opening choice is not dubious then there´s no problem, the fight is going to be in the middlegame and endgame.
what´s wrong with that? You just have to study the pawn structure, tactic patters and endgames associated with the opening.
Maybe you are not getting a winning advantage because your oponnents are not unprepared anymore, but it´s good for you since you can practice all aspects of the game.
I have read that Kamsky has a narrow repertoire with black:
"It's quite amazing how Gata Kamsky manages to score so well with such a narrow repertoire with Black. In his favourite Chebanenko Slav/4.e3 Grünfeld/Schlechter hybrid he equalized quickly against Shakhriyar Mamedyarov; the American used less than an hour on the clock!"
http://www.chessvibes.com/karjakin-on-22-in-beijing
Maybe in the future you are going to be able to save a lot of time in the opening phase of your games and have available time for when the critical moment arise! 
Hi,
I wanted to improve my rating (1700) with limited training time. I decided to only play 1 opening as white (English). I feel this approach will give me advantage as I will have so much experience on it and will understand it more.
At first i did get good result with it, but as time goes by, players in our club already know that i will be using english opening. I found my self loosing or i feel they are more prepared and my result is not as good as before.
Is it bad idea to only have 1 white openign as I'm loosing the surprise factor of winning a chess game?
Thank you and more power to Chess.com.