One thought process when you dream about mice is because you have the ability to tackle little things that niggle you in order to move on and deal with the bigger more important issues.
Another interpretation is that you might spend too much time on the little problems rather than the more pressing things.
If you saw a mouse in your dream it's possible that someone in your waking life is chipping away at your resources and or your self-confidence and it's slowly taking its toll on you.
The dream might be a reflection of your personality- perhaps you are timid and need to speak up more so people don't walk all over you or take advantage of your good nature.
Mice are also intelligent, compassionate and resourceful, so it's possible that you are able to turn weaknesses into strength and something that's seemingly disadvantageous into something advantageous.
If you were killing a mouse in your dream- your friends or family might be overstaying their welcome at present or you want your partner to move out- you have an unwanted guest in your waking life.
If you were frightened of the mouse, it's possible you are scared of something in your waking life that poses no real threat to you. It might be time to remind yourself that this person or thing shouldn't make you anxious.
Source: The Complete A-Z Dictionary of Dreams by Ian Wallace
Tagged in Dream Interpretation