The advice not to start a relationship before completing Step Nine is sound.
When I was messed up, I was going to have messed up relationships. A messed-up person can't have a healthy relationship.
A messed-up person has a broken picker and will pick a messed-up person.
Messed-up relationships tend to be vehicles where the messed-up person tries to fix the wrongness, guilt, and fear inside by finding someone to 'make them feel special', i.e. giving away their messed-up-ness and getting gold in return, except the other person is doing exactly the same themselves. Each is selling the other a bill of goods, feeling guilty about that, then shifting the guilt to the other person by finding things wrong with them and attacking them.
If, in the past, you've found things wrong with the person you're in a relationship with, you'll find something wrong in the new relationship, because the purpose of the relationship is to secure specialness but avoid the price by demonising someone else.
Only once that whole system is deactivated, by completing the first nine steps and setting out on an entirely new basis of relying on God is a healthy relationship possible.
Then, and only then, is it possible to do the two things that relationships are for: forgiveness and service.