What is the best strategy to change my Princess' mood?

Unlock more weekend activities and you'll have an easier time. If you study Dance you'll eventually get Ballroom as an activity and then you can raise Pressured more conveniently.

Your princess' mood is influenced by her weekend activities and by your decisions during special events. Sometimes, those event results are logical (for example imprisoning someone can raise your anger or depression), but sometime they are really hit or miss. You will get the hang of it with more playthroughs.

As for the weekend activities, you have access to the standard ones from the start. You can gain access to more by leveling your skills (e.g. dancing for ballroom, reflexes for sports, horses for hunting and more). And keep in mind that the effect of weekend activities can change depending on your current mood - visiting (for example) the dungeon when willful will make you more angry and willful, while visiting them while yielding will make you more yielding and afraid.