If you are confident that you have written well and deserve more than the marks you have received, then go ahead and request revaluation.

Even if you're not sure, take the plunge. It will not cause you any harm. The best of the two marks, that is, before and after the revaluation, will be considered, so there is no need to worry. You simply need to believe in yourself and go for it if you believe that the grades you received are inadequate and should be increased.