When someone who has joined Opus Dei considers that they cannot fulfil the commitments they freely took on, they can ask to leave. Permission is always granted.
When people join Opus Dei they freely take on certain commitments, which are briefly stated in a formal agreement. They commit themselves to try to live out their Christian vocation to the full in accordance with the spirit of Opus Dei, doing their best to imitate Jesus Christ in their ordinary lives. For its part, the Opus Dei Prelature commits itself to provide them with the necessary formation and spiritual help to achieve this goal.
To make these commitments validly people must be over 18, and for the first five years they can only commit themselves for a year at a time. At the end of those five years, when they are at least 23, they can make their commitments final and permanent.
Obviously, if anyone is thinking of leaving Opus Dei, they are invited to think their decision over carefully in God’s presence, since they joined the Work out of a conviction that God was calling them to this path. However, nobody is kept in Opus Dei against their will. When they formally request permission to leave, the request is always granted, including in cases of people who had been permanently incorporated into Opus Dei.
When a person leaves Opus Dei, they continue to have the love and prayer of all the faithful of the Prelature, and, if they so wish, spiritual help for their Christian lives.