How do you make a relationship last?

"I don't know. It just lasts."

1. Know what you want. When you know what you want, it's not easy (impossible in fact) to stray or get distracted.
2. Fall in love every single day. I know it sounds rather silly but yes, try falling in love with your partner every single day.
3. Do not be lazy. People think that love fades that's why one gets lazy; it is actually the other way around. One gets lazy that's why the love fades away.
4. See the positive traits in each other. Know that there's no one else like him/her.
5. Communicate. Communication is the bridge between two human beings isn't it? Be it verbal or non-verbal. Just communicate.
6. Quality vs. quantity. It does not matter if there's little time together. Make sure you make the best out of the little time.
7. Do not bear grudges. He/she is only human and human do make mistakes; albeit he/she should not be repeating the mistake.
8. Be transparent. Voice out your opinions, do not let unhappiness snow-ball till a stage where the relationship is irreparable.
9. Trust. Not having trust, being suspicious and needing assurance can prove to be high-maintenance and energy-zapping for the partner.
10. Love one another.

Disclaimer: This is not tried and tested. Try at your own risk.