"I'm really glad to hear that you are feeling happy recently! I am happy as long as you are too. So don't stop being cheerful! You are indeed the cutest!"
Hi! I will not translate English directly into Korea since it will be little bit awkward to native speakers. Therefore I will translate it more properly into Korean but it will convey the same meaning :)
너가 요즘에 행복하다는 말을 들으니 정말 기쁘고 너가 기뻐서 나도 정말 기뻐. 항상 기쁨을 잃지 마! 그리고 너가 정말로 가장 귀여워!