Just before I answer your question.
Correction: "How to have a long lasting relationship?"
And the answer to that question is :
- Be honest
- Turst one another
- Spend time together
- Understand one another
If you want any more help let me know :)
It requires sincerity on your part, and also on the part of another person.
The sincerity of other people is not something we can control.
If another person is insincere or selfish, any relationship will be either superficial