Sometimes interest is required, sometimes indifference is profitable. For instance you may be in a situation where you want to accomplish something, and people laugh at you; or perhaps people do not like you or are apt to criticize you. If you are interested in all these things you will lose your way. In that situation you should be indifferent. But if you have a business, and in order to promote it you have to see someone to get connections, all this will only succeed according to your interest. If you are indifferent about it you will defeat your own ends.