Yes, A devottee is always happy. Think of being a devottee to Krishna.....isn't the person happy being a devottee. His mind gets satisfaction when chanting than when doing any other thing. He/she starts getting out of Maya by becoming a true devottee. And by getting out of Maya, he gets the glory of Krishna.
My idea="A true devottee is always happy"
If I am wrong, I am sorry, and please say me about it.
Thank-you
Shuvo Roy