I believe that the requirement for confession is “within a reasonable period of time”. That gets debated as to what constitutes a “reasonable period of time”. I think that as long as one receives the sacrament (yes even if it is just confessing venial sins) relatively shortly before or after performance of the indulged action (within a few days to a week or so… maybe even 2 weeks if, for you, that is what is practically reaonable) that God will certainly be understanding and appreciative of the effort. Though if one is putting it off unnecessarily, well then perhaps they ought to question why and whether they are, themselves, detracting from the requirements for full (plenary) indulgence.
As to the detachment, I think it is just that, a firm commitment to avoid sin and devote oneself to a pure love of God. Being human, I suppose that it is questionable as to how long we can entirely keep ourselves in that state. But, then, that is why the Sacrament of Reconciliation is perpetually available to us and why the Lord continually offers Merciful indulgence. We’re always able to turn back and redidicate ourselves more completely.
In this sense, I would encourage you not to look upon indulgence merely in a legalistic way. Rather, see it as something which enables you to grow in love with God.