It must be remembered that
decisions are always made subjectively, and a person's state of mind before making a decision and after making it is never the same.
What this means is that
a decision cannot be criticised retrospectively, because the environment in which the mind operates at the time of the decision is not the same as the environment thereafter.
However,
one can attempt to analyse the factors existent at the time of making the decision later and surmise that a different decision could have given a different result.
The point here is this: it is absolutely useless to hold oneself guilty for one's previous decisions. It is, however, worth analysing the process which went into the decision so as to decide better (hopefully) the next time.
Yet, one can never be sure that one will decide better next time, because
the particular factors at the time of a decision are never identical. In fact one might find that reliance on a past decision is actually worse than deciding on the basis of the present. The past can only serve as the warning of a possibility which could result after the present decision.