First, you have to have a serious talk to each other about it. Admit to each other that the relationship is difficult and needs to be worked on. Get rid of the ideals of what it should be and start focusing on what's going on.
Talk to each other about what is making the relationship difficult. You might find out things that you are doing that you didn't know hurt the other person or was causing a problem. Some of these things will be trivial and can be fixed quickly.
Stop fighting or blaming each other for who the other person is. At times you might not like something about the other person. Getting into fights about it is not going to fix or help your relationship.
Consider planning some time apart. At times when getting to used to someone, problems occur. Separate for awhile and start appreciating who the other person is again.
Start planning simple dates where you can spend quality time with each. Do things that you can really get to know who the other person is or learn new things about each other. Consider doing new things that you have never done before and make it fun.
Talk about what you both want out of the relationship and even out of life. You can then see if your future goals are meeting up and if it's worth fighting for this current bond that you have with the other person.
Don't take the little things for granted. Start doing the little things that you did originally to get the other person to like you. These are things that should never be stopped so the other person feels appreciated and thought of.