These two things are vital for making any relationship work, but when you're miles apart, you need to trust each other completely and talk as much as you can. You sort of get into a talking routine when you are apart; you'll message them first thing in the morning and before you go to sleep, so when one of you misses one of those basic texts, the other will feel a bit worried and unloved. Something as simple as saying "good morning, I love you" will make all the difference.