i am happy that you are realizing the fragile state of marriages in our society today, and that you want to stay true to your vows.
1. i think the one single best thing you can both do is absolutely positively do not ever consider divorce an option (well, assuming you are both faithful to each other). i mean, don't even consider throwing in the towel just because you're not feeling in love anymore, or s/he doesn't make you happy anymore, or you didn't realize how selfish that person could be, or whatever else.
2. be aware that it is very normal and common to go through rough times. i have been married 20 years, and the last few years have been the greatest! we went through some horrible years, especially around 6-10 years, times when i was sure i hated my husband, we treated each other just awful, and perpetuated each other's nastiness. thankfully, through some excellent biblical counseling, we worked through things, and in fact, just tonight i told my husband "i'm so glad we made it through the hard years, because we would have missed out on how wonderful our marriage is now."
3. remember that loving someone is something you choose to do, not always something you feel like doing. (i thought i understood that before i got married, but i didn't have a clue). if you can each continue to act in a loving, respectful, kind manner to each other, even when you don't feel particularly "in love" for a period of time, (which as i said, is common) you will both eventually respond to the other's actions of love, and the feelings of love will come back.
4. you just simply cannot be selfish in a marriage. if you get focused on yourself, and she gets focused on herself, then you both end up feeling neglected and unloved. (even though you may both be getting whatever it is you selfishly wanted.) but, if you focus on her, and she focuses on you, then you're both still getting your needs focused on, but in a way that makes you both feel loved, rather than feeling like you're married to a selfish brat.
btw, i feel like i didn't explain that last one very well. i remember a time when one of my boys was asking me about the bible verse that talks about "do not look out only for your own interests, but also for the interests of others" and the one about "regard others more highly than yourself." my son wanted to know why everyone couldn't just look out for their own needs and interests, and wouldn't it end up balancing out the same? so i tried to explain to him that if he always did what he wanted, and his brother always did what his brother wanted, yes, it would balance out the same as if each of them tried to generally do what the other wanted to do. but the first way is based on selfishness, and the 2nd way is based on love.
i do hope that makes sense---a little hard to explain.