My sister-in-law cancelled my mom's birthday party on 24 hours notice, saying she had the flu, and that she’d re-schedule soon. Guests had been asked to bring gifts and wear costumes, so they’d already gone to some trouble. It’s been one month now, beyond a reasonable time to re-schedule.  
      I'm the only daughter and my mom's caregiver. My SIL approved that I could invite a friend, yet three days before the party, she said, "I hate her!” She later cancelled the party.
      When asked to help with the planning, I’d mentioned mom’s favourite colours, but they didn't match the decor.  My SIL invited people mom had never met. I wondered whom the party was really for.
      I mentioned going to a restaurant instead - disapproved. I offered to make half the food for the party. Rejected.
      I’ve been lied to, and disrespected. Worse, my mom has been hurt, disappointed and my SIL has embarrassed the whole family. She hasn't even visited my mom in 15 years!
      What started out to be a beautiful commemoration of my mom's 90th birthday, my SIL turned ugly over trivial matters.
      - Furious

Some “matters” here aren’t trivial – you two clearly have little warmth for each other, don’t communicate well, maintain a power struggle where “approvals” must be sought, etc.
      You’re good at making it all sound like her nastiness is at fault, so why would you think she’d easily make a party for a woman she never visits?
      My point: It’s the relationship between you two that’s all wrong, not just the party details.
      But that shouldn’t leave mom without a celebration. Call family members only (yes, including your SIL) and ask them to drop by and visit her briefly, and to bring a snack or treat, along with a happy attitude.

My parents divorced when I was six; I lived with mom, who smothered and spoiled me. At 15, I was forced to move to my dad (who hadn’t spoken to me in nine years).
      He’s very critical, controlling and passive-aggressive. A napkin improperly folded could throw him into a deep rage for days, and be raised as an issue years later.
      Going out was not allowed until he had ALL the numbers, addresses and names of my friends (I wasn’t doing drugs).
      At 21, I met a woman; we lasted for a year and a half until she cheated on me, leaving me broke and devastated. I had my own place, but then I got laid off. It threw me into deep depression.
      I’ve gained weight quickly, lost my self-esteem and have become uncertain about my future. Despite starting martial arts, driving and college courses, I’m still wallowing in depression from staying home alone for hours. How do I build myself up again?
      - Very Low

Keep getting out to activities and courses that can improve your mood and your situation. Also, approach job seeking as another activity: search online listings, update your resume, and find workshops that expand your skills.
      However, do NOT link these recent losses (a break-up, and lay-off) that are part of life for many people, to the disruptions and hurts of your childhood. There’s no link, no weighting of things against you, unless you keep perceiving it so and “wallowing.”
      You’ve achieved independence before, despite obstacles; you can do it again. Use every opportunity to get out, lift your spirits and connect with your inner resources – resilience and determination - that built you up before this, and can sustain you through difficulties.

I share student housing with four other girls. We each pay individual rent and split the utility bills. For the summer, the others are sub-letting their rooms; I’m not.
      One roommate suggested we collect the bills over the summer and later split them five ways. She told the sublets those charges were included with their rent. However, I won’t be using the utilities during that time. How do I make it clear that I won’t be paying for summertime bills without causing hard feelings?
      - Starving Student

Deliver your position with a smile: “I won’t be using the utilities and won’t have a sublet, so I’ll pay for my rent but you four will have to split those bills without me.”  
      They may rightly argue that you’re still responsible for utility bills that are ongoing even if nobody’s there, as part of reserving your room. You may have to compromise and pay half.