In today's day and age, sometimes it seems like marriages don't last. But you know there's nothing sweeter than seeing couples celebrate 20 years of marriage, or watching an older couple walk hand-in-hand. One thing is sure: marriages require work, but they are so worth it.

Here are six secrets to have a happy marriage:

1. Work out together

When you work out, your body releases endorphins, which make you happy. So it only makes sense to work out with your spouse. Not only will you be doing something active together and making memories, but you'll be keeping your body in great shape! Bonus points if you wear matching gym outfits.

2. Plan date nights

Whether you're taking care of your children during the day or you are swept up in a crazy work schedule, date nights might not happen as often as you used to. But date nights are critical to relationships. They help show that you're willing to make time for each other - just the two of you. Put on a cute outfit and look nice for each other. Dates don't have to be elaborate - you don't even have to go anywhere - but putting away the distractions (I'm looking at you, Netflix) for a bit and being together helps make your relationship a whole lot stronger.

3. Surprise each other

Do you remember the dating stage? When you were both constantly trying to win each other over with sweet surprises? Who says that has to end? Treat every day as though you still need to win your spouse over. Find ways to make them happy, whether it's through picking up their favorite candy or getting a babysitter so you can have a spontaneous movie night. You'll make their day and they will love you even more.

4. Recognize their weaknesses and love their strengths

Everyone eventually gets past the honeymoon phase, and it can be easy to start criticizing your spouse and notice their flaws. Recognize that both of you have weaknesses, and love them for their strengths (which are the reason you probably fell in love with them in the first place).

5. Appreciate the little things

Grand gestures are nice, but the key to a long-lasting relationship is to not take any of the little things for granted. If your spouse made dinner, put the kids to bed or filled the car with gas so you wouldn't have to, make sure to take notice and thank them. And be sure to do the same for them. Marriages aren't held together by flashy gifts and grand gestures, they're held together by the daily acts of love and affection.

6. Be open

Don't let small frustrations build up into giant explosions. The best way to have a strong, happy relationship is to be open with the other person. If the way they leave their clothes on the floor is bothering you, tell them. Don't get irritated and expect them to read your mind. Open communication is the key to making your marriage last.