From context, mainly. ESTAR I'm happy that my team won. I'm happy due to my team's victory. I'm happy because my team won SER I'm a happy person - ser The second is very clear and it is usually used with "person" because you are referring to a characteristic and not a temporary state. Also, note the use of the article "a" = sou feliz, sou uma pessoa feliz.

Se você tem o conforto Alba você feliz