Of course, every sentence you say need not radiate good vibes; overdone or insincere gushing would be counter-productive. But sprinkling a generous seasoning of positive expressions into your interactions can warm your relationships and brighten how people feel when they talk with you, whether you're dealing with a salesperson or co-worker, or a loved one or child at home.
Emanate positive vibes, even to yourself, and affection and appreciation will return your way. Everyone will enjoy the sunshine!
(Note: Giving positivity is one of four essential arenas of skills that keep relationships positive. Be sure also to develop your skills in the other three communication skill-sets (link is external). That way your smiles and positive words will express genuine inner feelings of well-being as well as outward expression of goodwill.)