to be very close friends
ser muy buenos amigos (ser mui buenos amigos)
"Those two have been thick as thieves since childhood."
"Esos dos han sido muy buenos amigos desde la infancia." (Esos dos an sido mui buenos amigos desde la infancia.)
to be declared healthy by a doctor
to give focused attention to something specific
to become happier or more cheerful
a sincere and open conversation
to keep working steadily on something
to deal with a problem when it happens, not before