Nightgypsy, fears were not part of the base game until after the high-school years EP. They replaced the old wants system that people disliked at that time. The current emotional state was a part of the game from day 1. In fact it was what they higly marketed the game to have as the centerpoint these sims. The way sims get into emotional states is based on how you play and they can be influenced by in-game objects as well as how sims act or even their traits. Later they even introduced lot traits that influence the emotional states. I am not saying how you play is wrong, but giving you the heads up on why it happens.
To get a sim the first level of playful, I actually have to really work hard at it. By doing multiple actions in a row that stack happy moodlets. Like I said, a majority of the time my sims only have the fine moodlet. I don't have mods that alter the emotional states either. One way to avoid it is to not allow so many happy moodlets to stack. One way to help is to purposely not always keep their stats green (like hunger, sleep, or even bladder and hygiene). If you allow them to go yellow and red, it helps to not have them always be happy which will stack to get to the first playful emotional state. Tjey are then concerned about fulfilling the need. I also do not allow my YA to elder sims to take purposely take baths. For some reason they always play in the tub if that is available, so I cue a shower to prevent it. I have only seen the very playful and hysterical emotional states when I worked extremely hard to actually kill a sim for my black widow challenge. That even took me using rewards points to buy the playful potion help me achieve it. Oh and there is a moodlet solver potion in the rewards store, if you really need it.