Interviewers ask - "why did you leave your last job?" And I'm never prepared enough for this

Please help me with a standard response you use for this question. I've been in 3 jobs till now. First - 21 months ; Second - 2Y 10M ; Third - 15 months. I just reach a point where I feel like I just cannot do this and leave it, then in a couple months switch. Also in two of these cases, my personal life got too overwhelming and I finally took the plunge. Last job was REALLY toxic (imagine screaming, yelling, drama) so that's another reason. I don't know what to tell when this comes up, I think as I talk and end up in a word salad, confusing them and myself. 😭