Don't be too clingy or needy. Strong communication. Spend time with his friends and family as well as your own. Have your own life and still share in his. And expect of him only what you're willing to give of yourself.
Mistakes? Do you mean adultery? Don't do it! If you mean other kinds of mistakes, don't get too cautious. An exciting life is more fun (I mean great parties and great friends, not adultery or drinking. ).
this is not an easy task to maintain healthy relationship with boyfriend for a long term. If you really want to build a good relationship with your boyfriend than first of all,make your nature sacrificing. this is a primary need of every boy that he wants that his girlfriend should be of sacrificing nature and adjustable.
1º of all don't call it relathionship...2º don't let your self fall in sick love. He will feel pressed and that means the end. Just let him be free. To choose you, to fight for you or just leave you, because thats better than be cheated... my opinion. comunication essencial.