DEAR AMY: I’m a single mother of three who has been dating a single father of three, on and off, for just over a year. We both have good careers.

I’m quite independent and levelheaded, with a positive outlook on life.

This relationship is an emotional roller coaster. We’ve broken up every few months due to my partner’s depression, lack of trust and negative outlook. He has been deeply scarred by his divorce and the several brief relationships he had before ours.

I believe he might be bipolar. His mood swings are extreme.

He told me he loves me and that I’m the best thing that has ever happened to him. He also says that I’m better off without him.

One day he is making grand plans for our future as a blended family. Then he suddenly falls into a depression — nothing is possible and the future is bleak.

Almost every week, he requires a few days of isolation to brood. He excludes me from helping him or trying to make things easier for him.

I love him very much, but we’re not getting anywhere. I feel like I’m failing him as a partner if I choose not to stick by him. I’ve become nervous and indecisive because his moods affect me so much.

A friend said that I’m obsessed with being his savior. I think I don’t want to give up on him, or our relationship, because I’m an optimist. Am I acting logically or rationally? I don’t know anymore. -- Deeply Confused

DEAR CONFUSED: One downside of being an optimist is that optimistic people tend to forget yesterday’s trauma in the belief that everything will turn out well. This can keep people in bad relationships because they genuinely believe that things will always improve.

Unfortunately, when it comes to people, patterns rule. Your guy’s black moods will return, and yesterday’s drama will repeat itself, no matter what your outlook is.

You cannot save him. You don’t have that kind of power. Unfortunately, he can ruin you — because black moods and depression trump a sunny disposition. He desperately needs professional help.

You have three children to think about. They are the ones who need a savior, every single day. If you can’t do what’s best for you, do what’s best for them.

DEAR AMY: I met my boyfriend a couple of years ago. We live together and share expenses. Just after we met he lost his job and his life started falling apart. I bailed him out by loaning him $5,000. When he found a job he paid back some of the $5,000 but after we moved in together, he stopped making payments to me.

He keeps talking about getting married and having kids and while I’m all for that, I’ll be really ticked off if he buys me an engagement ring before he pays back the loan (about $3,000) because every time I look at the ring it will feel like I paid for it myself.

I’ve reminded him a couple of times that he still owes me the money but he says things like “I’m saving up for something special.”

How do I handle this without ruining the whole “down on one knee” thing? -- Doubtful

DEAR DOUBTFUL: Ponder the math: He’s automatically supposed to drop thousands of dollars for a ring for you and unless he also repays you, you won’t consider a ring to be legitimate. And what monetary value do you give him if you get engaged? How about $3,000 worth of loan forgiveness?

Unless this is part of a pattern of bad financial habits on his part, if you really do intend to be with this guy for the rest of your life, then let it go.

DEAR AMY: I’m responding to “Frustrated and Trying’s” letter about newlyweds being asked when they will have kids.

I remember well when my grandparents asked my wife and me when we were going to start a family. We didn’t want to have children but at the time it wasn’t something we would share with others.

Whenever my grandparents asked when we would start a family, our response was always, “We tried just last night.” Boy, did that make the subject change immediately. -- Elder Reader in Boston

DEAR ELDER: Bam!

Amy’s column appears seven days a week at www.washingtonpost.com/advice. Write to Amy Dickinson at askamy@tribune.com or Ask Amy, Chicago Tribune, TT500, 435 N. Michigan Ave., Chicago, Ill. 60611.