A person who has a very casual attitude about things in general is said to have a devil-may-care attitude. This individual is rather carefree, and doesn’t get terribly worked up if things don’t go according to plan. He is rather reckless and doesn’t really worry about the consequences. The expression is considered to be rather old fashioned. It is also possible to say, `devil-may-care manner’.
*When it comes to his studies, Sandeep has a devil-may-care attitude.