Loner sims get less tense around strangers if they introduce themselves and interact a bit.
Detective Career: Have your sim introduce themselves when out looking for a suspect. If you know a suspect's trait and your sim doens't have the Observant trait yet, use get to know. If the sim they're talking to fits all the criteria and gets tense, they're likely the suspect.
I let noncommital sims build up both friendship and romantic bars to near full before tryintg to marry them off. That way they seem to be less likely to get tense.
It is possible to have a chlid or teen listen to music while writing in their journal. They gain emotional control, creativity, and fun from just two actions. I also let them listen to music while doing homework if their fun need is either about to turn yellow or already yellow.
That's all i can think of right now.