The "Fourth Agreement " is " Always do your best"
Don Miguel Ruiz says, "The fourth agreement is about the action of the first three agreements but it's the one that allows the other three to become deeply engrained habits. The first three agreements will only work if you do your best. Don't expect that you will always be able to be impeccable with your word. Your routine habits are too strong and firmly rooted in your mind. But you can do your best. Don't expect that you will never take anything personally; just do your best. Don't expect that you will never make another assumption, but you can certainly do your best. By doing your best, the habits of misusing our work, taking things personally, and making assumptions will become weaker and less frequent with time. You don't need to judge yourself, feel guilty or punish yourself if you cannot keep these agreements. If you're doing your best, you will feel good about yourself even if you still make assumptions, still take things personlly, and still are not impeccable with your word."