At the end of my rope (expression)

Meaning:

Imagine a dog who wants to attack a cat. Imagine that dog cannot attack anything because he is on a rope. If the dog pulls so he is at the *end* of his rope, he is *almost* free to attack the cat.
As humans, sometimes we want to do aggressive things too. But we must use our minds as ‘rope’. To be good people, we use strength and patience to control our aggression. But sometimes people push us too much and we lose our self-control. In that case, we can say, ‘I’m at the end of my rope!’ This means: ‘Be careful around me! I have almost lost all my patience and maybe I will become angry if you say the wrong thing.’