As excerpted from Holy Protection Orthodox Church.

Prepare for and go to a meaningful and well-prepared Confession at least once during the 40 day fast of Great Lent (i.e. before Holy Week). Well prepared means doing a full examination of conscience, such as found in prayer books, or the following link. 

Read Confession Hours for Lent 2024

Why before Holy Week? 

Great Lent and Holy Week are distinct from one another and have different purposes.  Think of it this way:  For the 40 day fast, Jesus gives each of us “me” time to work out our own salvation.  So Great Lent is “us time”, but Holy Week is “Jesus time.” 

Great Lent extends from Clean Monday until the Friday before Palm Sunday, and that is the time where we are to focus on us getting right with God so that we can rightly celebrate Holy Week and Pascha.  All of the midweek services are penitential in nature, and it is a natural setting for the “big” confession of the year. But from Lazarus Saturday/Palm Sunday onward, the focus is on Christ.  

In other words, the Church gives us 40 days to deal with our “own issues” and sins, and get them out of the way so that we can at least give one week (Holy Week) focusing solely on Christ.  We should have already laid our sins at Christ’s feet before Holy Week, during the Great Fast itself (again, from Clean Monday to the Friday before Palm Sunday), because the purpose of the confession is so that we are ready for Holy Week when it gets here!  Thus, we should have already made our “big confession” during Great Lent, and any confession during Holy Week should be rather brief and supplementary.  Good times to do one’s Lenten great confession is before or after the midweek penitential services such as the Penitential Canon and Presanctified Liturgies (it is best to give the priest a “heads up” if you want confession more than a half hour before the service starts by email or text, since he has preparations to do and has to adjust these preparations to hear confessions).  Also, Sundays before the Liturgy (before 9:50am).