Regret

One of my cousins contacted me couple days ago for a job. Well i ask for his academic transcript like usual. Kinda disappointed with his gpa though. It is quite small. So then i start thinking, aside from someone capability, do we always regret what we do in the past? I mean is it always late for a regret?
We are going to school and not study hard enough. What kinda mechanism that available to make us regret faster, faster enough to change the situations? I don't know the answer, may be someone around you? Your parent? But if we are the parent, then what is actually that we should do to make this regret doesn't come late? Not sure about the answer.

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@Mobile