Catholic Spiritual Direction has a great post and “self-test” about discovering our predominant fault. Identifying our root sin (or predominant fault) is key to growing spiritually, but it isn’t always easy or obvious. Father Bartunek explains the whys and hows well. The self-test offers key questions to help us narrow it down. (We will likely find ourselves in all three of these, but one will typically be predominant.)
I encourage everyone to read it.