To firmly or stubbornly adhering to one’s purpose.
Person can be characterized by inflexible persistence or an yielding attitude.
But since he had been in work he had become more obstinate and would always insist on staying longer at the table, even though he regularly fell asleep and it was then harder than ever to persuade him to exchange the chair for his bed.
This is when someone stick to what they believe in, refusing to change on how they feel about their opinion. This can cause the person to come off as stubborn. It may be hard to change this person gut feeling.
Source: http://dictionary.reference.com/browse/obstinate
