Terarria can be played as casual or low stress. You choose when to advance the difficulty, and how elaborately you contruct your preparations for the next step. But for a largely stress-free casual playstyle, focus on being a summoner. Also, there isn’t much penalty for dying. So if you can wrap your mind around not being bothered by dying, then any playstyle can feel casual really. It’s certainly a tough mindset to achieve for some of us though, lol.