Being a designer you can never be certain of anything you build, like science, good design is built on uncertainty.
Society perceives a lack of confidence in ones own work as a sign of weakness or questioning a tried and tested theory as unthinkable, yet in reality without questioning what has already been discovered or your own work we would still be in the stone age. People accepted that the Earth was the centre of the Universe for hundreds of years until some chap called Galileo came along and challenge it, Ethan Marcotte questioned the idea of a fixed width websites and responsive web design was born. Uncertainty breeds better solutions and world-changing ideas.
“If we knew what we were doing, it wouldn’t be research” – Albert Einstein
Great web designers accept that they don’t have all the answers, but understand that through questioning, researching and iteration they can devise great resolutions for current problems. However the issue is things change, what works now might not be right for tomorrow. Technologies update and client bases shift, so by being open-minded to this lack of certainty in everything great designers will always fight to understand how they can create better products with the information they have now.
Being open to new ideas and having the courage to question, revise and break down your own work leads to even better creations. Using research, thorough testing methods and gaining feedback will only bring more questions and in turn greater uncertainty, but that’s fine. Embrace it, ask more questions, find better resolutions and repeat.