Mentoring is one of those "out of the spotlight" things many better Doms almost automatically undertake.
There can be valuable rewards in helping a sub overcome old wounds, some deep and damaging still. Other kinds of mentoring might involve encouraging or supporting new education or job training, assisting with upward moves, setting and helping goals in weight loss or better exercising. The list is endless.
What I am suggesting is that Dominance doesn't have to be purely sexual, or purely about "controlling" your sub by being some aloof dictator. It can be a much broader influence on her (or his) life. Mentoring involves becoming more aware of discomforts, old wounds, or deficiencies felt by your sub. Once the Dom/Domme becomes aware of those things, the focus can shift to "How can I help?" mode. This can be as little as encouraging and offering sympathetic support. It might involve laying out protocols which bring some improvement to your sub's emotional or physical life. Sometimes it might even involve financial assistance. Yes, sometimes even tough love may be required.
The point here is just that Dominants can make a real difference in a sub's life beyond what's generally discussed within our Cage.. It only takes paying more attention, and wanting to widen our influence in making our sub's life better than when our relationship began.
Feeling you've done that for the other in your D/s relationship can be most rewarding to any Dom who gives it attention and effort....