Why do I mix past simple and present perfect when speaking?

Because the two forms are stored as one habit rather than two rules. Under time pressure you retrieve the form you use most, then the time phrase arrives and contradicts it. Working from the anchor removes the conflict, because the window is chosen before the form and cannot arrive late.

Recordings change what you can notice. In conversation the mismatch passes in a second, so the habit never gets a fair hearing; on a recording you can stop at the exact sentence and hear the anchor and the verb disagree. Three one-minute recordings over a week give you a short personal list of the two or three anchors you handle badly, which is a better study plan than a full tense chart.

Present Perfect or Past Simple? A Rule You Can Use While Speaking →