At the beginning when I started playing Sims 4 and I didn't have much experience on game play I created a family, parents and two kids. I forgot to make the parents married in create a Sim and I thought I'll just quickly make them have a romance and get them married, instead of just restarting the game (after fixing their relationship in CAS). I quickly maxed their romance bar and friendship bar and made him propose to her the next day after starting the game. She said no... and he got mortified and died.
I learned a lesson to never propose too quickly, but I still get nervous every time my Sim proposes.