Dear Sarah,

The exact answer to your question will vary from order to order. There are some orders that would leave such decisions entirely to the individual nun, but this is not usual.

The essence of obedience is to put yourself in God's hands, out of love and full of trust, to do his work under his terms. The means God uses to speak to a nun or consecrated person are not so much her personal feelings or likes, but rather the example of the Foundress, her spirit as expressed in the Rule of the order, and the desires of her superiors. So she will be more concerned with how she can better live that spirit than her own personal considerations or preferences.
 
When you are in a community you also take on certain obligations towards the others, they have to be able to count on you to do your part selflessly towards the particular aims for which the group was approved in the Church (teaching children, caring for the sick, parish catechetics, etc.) even if your feelings change or you are getting tired of some particular aspect of the work. There is nothing unusual or out-of-this-world about this, the same goes for any mature person in a life-commitment, such as a married person.

None of this prohibits a sincere openness with one's superiors, and there are times when change is good and necessary, but obedience is to want what God wants. Sometimes what he wants will coincide with what we would like and would have chosen ourselves spontaneously, and sometimes it will be very different. But true obedience when we do it out of love is always joyful and optimistic, because we know we are in our Father's hands and he wants what it best for us and for everyone.

God bless.