You're nervous about approaching the Cullen house. Carlisle has been trying to get in touch with you, and you've been purposefully avoiding him. You mainly live your life on the road, so you can it make it difficult for people to find you, but Carlisle would know how.

 You received a letter from him, asking you for help. The Volturi are accusing his family of something they didn't do, and he wants you to be one of their witnesses. You know whatever it is they're being accused of, they couldn't have done it; the Cullens know better than that. So, whatever's going on has to be something dangerous, especially if they were going around asking everyone they know for help.

 Your reason for avoiding Carlisle is a personal one. You used to have feelings for him, but it was obvious from the beginning that he never felt the same way you did. Now he has an entire family, and you're still on the road by yourself.

 However, as you read his letter over and over again, rereading the words in the neat handwriting, you realize how serious this could be. Carlisle needs help, and he's asking you for help. How can you deny him and his family that help?

 You get in your car and drive to Forks without stopping once, wanting to see Carlisle that much. You're a little excited and a little nervous; you haven't seen Carlisle in years, and you don't know what exactly you're getting yourself into.

 You are most certainly nervous when you finally reach the Cullens' and park your car outside. This is where he lives happily with his family, something you had once thought the two of you could have together. You have a feeling of anger and jealousy as you walk up to the front and pound on it.

 If any of the other Cullens answered the door, you probably would have continued to be angry. But Carlisle himself answered the door, and all your angry feelings went away when you looked at him.

 "Y/N. Did you get my letter?" he asks. "I'm glad you're here."

 You don't say anything. You simply wrap your arms around him and hug him.

 "It's good to see you, too," he says. "Here, come inside. There's a lot of people for you to meet."

 All hard feelings you had when you arrived disappeared. You can't bring yourself to really be mad at Carlisle; you still feel too much for him for that.