Failing as a parent

Do you ever feel like you are failing as a parent

I have two children oldest being nearly 6 years old and the youngest is 18 months

My oldest is doing my head in at the moment just not listening to anything we tell him constantly getting into terrible around the house and my youngest has started to not listen as well.

I just don't know where I have went wrong I know it's been a hard year for everyone but I didn't think it would change the whole why my children act