Voted Best Answer
Oct 12, 2015 - 10:40 PM
Another example. The girl at the store was beautiful. Here I would use ser, because you'd think she's always that beautiful. But let's say she had blue hair and you don't really like this, you could say "Esta chica es muy bonita pero creo que hoy no está guapa con este pelo."
For me, the SER/ESTAR problem has gradually been easier to cope with by listening to what people say. My Mexican friends correct me all the time, and even though I am starting to get a better grip on it, the wrong usage often slips in when I'm in a conversation. However, less and less. I don't think i'll get it right all the time, ever, it's frustrating, I know, but don't hesitate to ask natives when you're not sure why they use ser instead of estar or vice versa in a conversation.