Parents need to be consistent in their use of discipline. If you say to your child “you’re grounded for a week,” it is critical that you follow through with that consequence. If, three days later your child asks to go out with friends and you allow it, the consequence has not served its purpose.
Often, just the fear of being punished is enough to deter our children from misbehaving. By not following through and not sticking to your word, you have also compromised the fear of punishment as a deterrent. Your child may well assume that since you didn’t follow through with the consequence last time, you won’t next time.