Quit criticizing, cajoling, threatening, pleading, moralizing and in general acting like his parent. If you want him to be adult, treat him like an adult by insisting on responsibility and not shielding him from the consequences of irresponsibility. If you act like a parent, he will continue acting like a child. It doesn't help him and it only makes you more miserable. There is only one time when intervention can be effective and that is when it is requested.
Advice is difficult enough to take when it is requested.
Unsolicited advice merely strengthens resistance by implying a superior-inferior relationship. Don't offer to assist the loser do a single thing unless he requests that assistance. You may inform him that you have resources available to refer him to, but don't offer them unless he requests them. If assistance is requested, the next step is to make sure you don't fall into the trap of becoming responsible to follow through. The most you should do is tell him where the phone book is located.