Rule #1: Marry the one you love
Rule #2: Love the one you married.
You may break Rule #1, but never break Rule #2.
For a happy marriage live, you marry the one you really love. Sometimes, it may not that perfect that you get to marry the one you really love. There may be situations that prevent you from marrying that person and you marry someone else instead.
However, what is more important is Rule #2. Once you are married to someone, make an effort to love the one you marry. Even if you did not really love him or her at first, make an effort to keep the love growing.
There will be new differences that you had never encountered before. Respect that differences in the one you love.Your opinions will differ. You like different things, different food, different places, etc.
You may encounter lots of situations where you may wonder is that the same person you loved before. What made you loved him or her? For a happy marriage, loving another is a continuous effort. It needs constant communication, care and energy.
What ever happens, make an effort to follow Rule #2.
Wishing you long lasting happiness with your spouse.