The best thing to do when you miss someone is to tell them. Show them how much you care and love them. Many people ended up in having regrets in their lives for not taking the chance to do so for their loved ones, they waited for the right time to come for them to say so. Time waits for no one. If the three words are just so hard to give away, make sure that the other person(s) recognize(s) your unuttered feelings.