Whether it is surprising her by cooking her favorite dinner or sending her flowers at work, small gestures like these show your girlfriend that she is on your mind and that you care for her. Every woman needs to be reminded of how beautiful, smart, funny, or interesting she is. Don't stop complimenting her just because you have "won her over" and are already in a committed relationship. Do it because you mean it, and because it will make her feel more confident and loved. Maintaining a healthy sex life will help keep the relationship alive. If you are worried that the sex is getting boring or that your girlfriend is unsatisfied with the sex, then maturely bring up the subject with her.  While this may feel awkward or difficult at first, it will be well worth it in the long run if it improves your sex life! Wait for the appropriate moment. Don't bring up the issue in public, in front of other people, or in a joking manner. Joking about the topic might make your girlfriend feel embarrassed or insecure.

TL;DR in Chinese:
玩玩浪漫. 给她做一顿她最爱的晚餐也好，送花到她单位也好，这种小浪漫可以让她知道她在你心里有多重要，你在意她。 称赞她. 每个女人都需要被提醒她有多美丽、聪明、幽默、有趣。 对性采取开放的态度. 良好的性生活可以给爱情保鲜。