TDD is very important skill you have to achive as a programmer. As a professional you will grow every day and every month. Every time you learn something new and every year you see your legacy code you feel like you would change it with your new skills. But when there is no tests you wont do this at all. Becuse of fear described before.
But with tests written before you will do rewrites. (Sure not for all code, but just for code you touch for changes)
You will be free in refactoring your code with new knowledge and with new architecture decisions. And even with new business rules for your code.
And on the rewrite day you will measure how really TDD is important.