The hardest part of learning someone new is that you are no longer in your comfort zone, buttons do different things and are used differently.
Noel's 5B is for spacing, Lambda's 5B is more close range.
Noel's 2C is a low, Lambda's is an anti-air.
everything is so different, especially true when you are going from Zoning(Lambda) to Rushdown(Noel) where the entire point of the character is different, as Lambda your goal was to keep your opponent as far from you as possible, but as Noel your goal is to chase them down.
Point is: Don't give up, because you become a better player if you can get used to playing multiple styles, and as an added bonus you'll find out that you will also get better with using your main character by playing a sub as well, since it will give you a new outlook on the game as a whole, and find new ways to deal with a situation you may have only previously had one answer for.