Q. Where in the world did you get your indefensible position, "There's no such thing as a good divorce?" writes a woman in Prince William County.

"There are hundreds and thousands of good divorces, even if children are involved.

"You really laid the guilt on the poor soul who wrote that she wanted out of a miserable marriage to a workaholic who was insensitive to all her needs.

"Do you really think children are unharmed by living with two adults who hate (not too strong a word) one another?

"I know what a happy marriage is. I had a great 20-year marriage, which ended when my husband died. Then, one year later, I married again. That was two years ago. This marriage was full of arguments, personality conflicts and discord. Yes, we tried marriage counseling. This was especially true in my case, because I don't have many years left. So I chose divorce. I am very, very happy.

"Yes, there is such a thing as a good divorce." A. Just because a divorce is necessary doesn't mean it's good. Even though it's the start of a new life, it still hurts to get rid of the old one, however unpleasant it was.

You may feel relieved afterward, even for a time euphoric -- as if you had stopped hitting yourself on the headwith a hammer -- but any divorce leaves scars.

You were able to make arealistic decision because you had had the chance to compare the sweet with the bitter and because you had tried counseling too. Many other coules don't have this experience or guidance or were even able to watch their parents survive the tempests of their own marriage.

It's hard for these couples to tell the difference between a rough patch and quicksand so they may think that divorce is obligatory when it is only inviting.

If after counseling they must choose that route, as your did, at least they should know that the more they have invested in a relationship -- in time and effort and especially children -- the more it will hurt to pull it apart. Q. The one problem not mentioned in your article on baby sitters is one which I have been experiencing in the past few months," writes a Fairfax mother.

"Several of them accepted jobs a week or two in advance -- obviously very important occasions for me, and I think I made that clear to them. A couple of days before -- or a day, in one case -- they have called and canceled. Substitute sitters were offered, but they were not sitters I wanted to use. Even if they were, I felt they were very irresponsible to change plans.

"I have understood it before when the sitter suddenly couldn't come and was obviously upset, but the last few times these new sitters -- younger sisters of the ones I used to hire -- have treated the dates very casually. When I told them how upset I was they seemed genuinely suprised.

"Am I too rigid? It's very hard to make plans under these circumstances."

A. It certainly is irresponsible of them and you do need new sitters. The welfare of your children is your main job; you can't pass it on lightly. If you can't trust a sitter to keep your date with you, you're bound to wonder if she will follow your rules if she does show up to sit.

While it is a sitter's duty to keep a date, it is your duty to make it clear that she must.

Tell your next sitter that you have been burned before and want to know if she ever reneges on her sitting dates. If so, you will have to look for someone else. When a parent clearly expects professionalism of her sitters, she is much more likely to get it.

From Alexandria comes an annoyed reader who feels we booted a recent reply. Like an earlier correspondent, she felt the Three who had turned into a "monster" was reacting to nursery school.

"As a teacher, I have observed and worked in nursery schools where I would not leave my dog. Poorly paid, frequently changed, inexperienced people would treat children one way when parents were there and another when they were not. I would never enroll by children in such establishments.

"You seem to have some pitfalls in proclaiming yourself an expert, to answer as rudely as you did." A. This letter is not what the Landers lady would call a day-brightner.

We're not quite sure why our answer seemed rude, but apologize just the same. As for the nursery school, we thought it went without saying: A parent only puts the child in a school after checking with other parents, observing teachers carefully and seeing if the children look happy to get there.

If the environment is good -- or even pretty good -- a Three will profit more by being with other children those nine hours a week than he will by being with his parents on a nonstop basis.