After an 18-months “break,” my girlfriend and I decided to try again, this time discussing building a life together.
Moving in together was challenging: I’d been single for a long stretch before dating her; she had two kids, a rocky relationship with her ex-husband and a mother constantly voicing her opinion. Stress was always present as I tried to learn the rules of having an instant family.
Mostly, we were able to diffuse any issues. But we’ve been three weeks apart now, due to a small misunderstanding that grew rapidly. I find that missing them makes the days go by slowly.
The issues were from outside the relationship (work, parents, money).
I accepted the duties associated with the children, as I enjoyed the family atmosphere very much.

- What Now?

Correct the misunderstanding, and tell your girlfriend how much you miss her and the family life. This will be reassuring to her, but it's not all that's needed.
"Work, parents, money," like all issues that stress a relationship repeatedly are NOT outside it, they're part of the whole deal. You two need to find a strategy for facing problems.
Your adjustment to children was only one necessary change. What are the other compromises going on, from both of you? How is she handling her intrusive mother?
If sharing expenses was a sensitive area, did you divide your incomes proportionately, and/or get advice from an accountant.
You'd benefit from couples' counselling, to air out these issues and learn ways to reach solutions.

My mother had been dating a guy; they never told me that he had two kids, nor that he was still married (although separated) but living with his now ex-wife when he started dating her. Eventually he moved in.
His family immediately began stalking our house, leaving messages, etc. My mother moved to another house, to escape the stalking.
Meanwhile, her boyfriend turned into someone else. He was controlling and hurtful, yet my mother never stood up for me, though she stood up for my brother when he visited. She’s since apologized, as she saw the physical side effects on me of his behavior - I began to have panic attacks and had trouble eating without getting ill.
Several years later, I’m fortunately now healthy and happy. But whenever I visit he pretends everything’s normal, which makes me really uncomfortable.
How do I get my mother’s boyfriend to apologize? I want to continue seeing my mom.

- Conflicted

Don’t prolong the negativity of the past from this guy, by waiting on an apology that may never come. The relationship to care about is that with your mom, and she has acknowledged that she let you down. Visit her on her own, if you’re so uncomfortable with him… meet her for lunch, or take her to a movie, go for walks together, etc.
If either of them ask why, be upfront that you still hold him responsible for several difficult years in your life; and that if he wishes to acknowledge that to you, you’d be willing to listen.
But to stay healthy and happy, don’t allow the past to rule your mood or your current improved communication with Mom.

My son’s girlfriend has a brother who’s had cancer. Isn’t it my responsibility to warn him about the possibility his future children will inherit these unhealthy genes?

- Worried

No. Look into your own gene pool and recognize that all of your relatives who passed, had something.

I’m 17, an atheist, and I recently told this to my best friend, a devout Catholic. She didn’t take it well, saying it’s the road to corruption, and sure to be just a phase.
I’m disappointed and angry at her lack of tolerance, and am concerned about how the friendship can continue after this blow-up.
I greatly value her friendship, but I’m unwilling to sacrifice my beliefs for it.

- Wary

Drop the topic, and return to the many others that made this a valuable friendship for you.
Part of maturity is not only being committed to your own belief system, but comfortable enough to not need to share it with everyone, especially where you know there are fixed, contrary views.
Your friend may never have faced this approach before: IF she’s curious, explain your beliefs. But if she then remains judgmental and can’t leave the topic alone, you’ll likely not stay friends.