12 Ties that Bind Long-Term Relationships by Susan Krauss Whitbourne,

1. Thinking positively about your partner. Having positive thoughts about your partner means that you focus on the good, not the bad, in your partner’s personal qualities and character. Ruminating about the things that bother you can only lead you to magnify the small foibles which will make your partner even more irritating to you than you would otherwise feel.  People in good relationships engage in “sentiment override,” meaning that they remember more of the favorable than the unfavorable experiences they’ve shared together.

2. Thinking about your partner when apart. When you leave your partner for the day, the evening, or for an extended period of time, do you forget about his or her existence? Is it out of sight and out of mind for you? If so, this may be a sign that you’re not that much in love. You don’t have to spend every second apart sighing longingly, but the fact that your partner isn’t there should at least cross your mind some of the time during the course of the average day.

3. Difficulty concentrating on other things when thinking about your partner. If you’re able to set aside your thoughts about your partner without much effort, this suggests that your partner takes up only a small amount of cognitive load.  Multitasking isn’t particularly desirable when it comes to musing over your loved one. In the O'Leary study, this factor was particularly important for men.

4. Enjoying novel and challenging activities. Like definitely attracts like when it comes to personal interests and hobbies. Spending time together is important, as you’ll see below, but it’s how you spend your time that influences your relationship satisfaction even more. Aron’s self-expansion model, tested in empirical research, suggests that couples can improve their love for each other when they spend their time together exploring new and challenging activities. The O'Leary study identified this factor as especially relevant for men. If you’re going to go bungee jumping for the first time, your relationship will benefit when you and your partner face this challenge together. If you’re not up to bungee jumping, seek out mentally challenging ways to spice up your daily routines.

Read the complete article at Psychology Today