Even Mattie does not have a lot of money, as she is dependant on peoples good will since Zeena decided to get rid of her when she worked as a servant for the Fromes. When you have a lot of money you seem to have a lot of freedom but when you lack it, you seem to be "imprisoned".
Your loved ones well being is important and can affect your mood and the way you are. Ethan has been surrounded by sickness since he was in school. His mother was ill and due to that he had to drop out of school since his family could no longer afford it. Ethan had to be on call for her mother and work as wel,l just as he is doing now. He is on call for Zeena 24 hours a day. All the money he makes goes to her medicine, and he is constantly pressured by her. He feels an obligation towards her because of her sickness. He even wants to run away with Mattie because of her. Ethan is not happy with Zeena and the constant bad mood that she is in. Ethan has not been happy for years and he finally can see an opportunity for happiness and an opportunity for actually having a life of his own. Zeena's mood is an important factor concerning the actions Ethan is taking, and he will not stand for it. .
Besides the mood of your loved ones, the location also makes a difference in people's mood. Starkfield is a gloomy place, very dark and quite cold most of the time. Some of the physical description that we are given is that it is "rocky, cheerless and dark". The amount of snow and cold plays a huge role in Ethan's mood. The way that the horses have trouble pulling the sleds is the same way that Ethan feels. Ethan feels a great weight on him already from Zeena and the weather and location just increases his constant suffering. The setting and weather isn't only a burden for Ethan as it is the same for all the characters, but it is more obvious in Ethan's case.
One factor that is particular in Ethan's case is his inability to communicate.