In wedding planning, as in life, you are bound to make mistakes. Not all decisions come easily, especially ones made under pressure and time constraints. Recognizing errors early so you can correct them and not getting bogged down with the notion of perfection will alleviate some of the pressure. Once you notice that something doesn't seem to be going right, take steps to navigate in a better direction. Ask family, friends, and/or vendors for their help where appropriate. Remember that your vendors want you to have a positive experience with them, so they may have good ideas and suggestions for you. Experienced vendors probably have seen it all and your problem area may not be new to them. It can never hurt to ask. And if they can't assist you, maybe they can recommend someone who can.
Another important concept to remember is to give yourself permission to make mistakes. We are all human and we all make mistakes, big and small. By allowing yourself this margin for error, you take a huge burden off your shoulders. You will experience less anxiety and stress because you do not submit to the pressure of having to do everything perfectly. Write yourself a wedding planning mantra to read daily giving yourself permission to make mistakes, to not feel guilty about them, and to enjoy your wedding despite any imperfections.