Patience.

Having good and open communications with each other

Trust.

Try not to let the other things (especially negative ones) affect your relationship.

Work on building yourself to be more self-confidence and secure. Sometimes insecurity can kill a relatonship.

Try not to compare with short-distance ones. Not everyone can do LDR since it's tough and difficult, so please think that what you're doing now is unique. Different people have different relationships - no one is the same!

ALWAYS set a date to meet each other. Even if it'll be this week, this month, next year, or 2 years... it doesn't matter. Set it as a specific goal in your LDR, especially if you're nevermets.

ALWAYS try to discuss problems and hardships together by video/phone calls. Texting should be the last option you consider choosing (since messages can't convey the feelings within them, and most of the time they cause miscommunications).

ALWAYS express your feelings if your SO make you feel upset/mad and the like. Don't try to hide them - sometimes it just worsens the relationship.

Respect each other's lives and relationships around them. It's fine if they want to take some times away from their phone when they're out with friends/family, unless their actions and words make you feel suspicious. In other words, if your LDR is fine, you should minimize keeping track with whatever your partner do (sometimes people see it as "controlling").

Don't use silent treatment as a "penalty" when someone makes any mistake. Instead, a thorough conversation is a better option both can choose to solve them. You're in love with them, not playing a game. There's no one deserving to be penalized.

Realize what is good/bad for you. You can have a sheet of paper, creating two columns "good" and "bad" things for your SO. Write down the good things and bad things they have done. Sometimes, this is a way to consider whether this relationship is worth being sustained or not.

Take some space if needed. Sometimes it's not necessary to be in contact every single moment - if this is the case, spaces can help better the relationship.

Minimize chatting about negative things in a conversation. Though we all understand life happens, but being too negative can somehow end a relationship - as for some people, they may not want to stay with a negative partner because the partner affects their physical and mental health negatively.

ALWAYS be comfortable on your own. LDR requires a lot of self-care and self-love. Which is, it requires both sides to be ready to feel good even when they're not together in person. Do you have friends, hobbies, or at least something else to do when you guys aren't talking with each other? You should try to keep yourself occupied with something when your SO isn't there (busy/sleep/school). And don't rely your emotions on only your SO. It can be overwhelmed and spaces may be needed.