I've only been married for 4 months but I've asked many couples whom have been married for 20 + years what their secret to success has been. Here are some of my favorite answers...
1. Never lose your try. When you dated your spouse, you went out of your way for them and Always tried your best. Be careful to never lose that. Never grow comfortable.
2. R.E.S.P.E.C.T - always respect your spouse. Place them in high honor. Don't ever call them out in public either. Correct them privately.
3. Keep God at the center of your marriage and it will go well for you.
4. Make Lots of Love - Sex is not just an act of pleasure . It is an act that brings an intimate bond between a husband and wife every time they have sex. Sex in its purist form will give you a connection in your relationship that will be incomparable to any other relationships you have. So husbands, wives, enjoy each other..... A LOT.