As a new parent, enforcing discipline is really tough because kids are cute and cuddly. Everything in your being wants to make those children happy at all times. The mere nature of discipline being what it is, they are not going to be happy. Establishing firm, fast and consistent forms of discipline very early, I think, is very important. Long term, your children will respect you a lot more for providing them firm boundaries and guidelines for their lives; and I think it makes for a healthier relationship overall.