Ser and estar are tricky for anglophones. Here's a simple way of looking at them, for beginners:
Use ser for permanent attributes, and professions regardless of whether they are permanent.
Juan es fuerte. Juan es fontanero.
Use estar for non-permanent attributes, and locations regardless of whether they are permanent.
Juan está enojado. Juan está en Miami. Miami está en Florida.
That said, what we call 'permanent attributes' usually means defining traits of things or people, and what we call 'non-permanent attributes' means states/statuses of things or people. Being strong is a defining characteristic while being angry is a state. Some adjectives accept either verb depending on the meaning. For beginners, however, it's often helpful to think in simpler terms and try to follow these basic guidelines.
Here's Dan explaining ser and estar in a video: