Look at the chages you're making to the code - are they of a quality comparable to what was already there, do they integrate cleanly, are you coding with a style that fits in with the surrounding code?

If not, what could you be doing better and why aren't you already doing it? It may take longer in the short term, but give consideration to your development practices. Eventually you'll find yourself more quickly writing a higher quality of code that's more maintainable with fewer defects.