If I recorded, mixed, and produced your album, you no doubt have heard me say, I will not Master your album.  These are words I say often, yet I also offer a Mastering service.  Strangely enough, I get a lot of Mastering business.  Why is that?  The answer is quite simple and effective... assuming the goals are for maximum quality.  "No one is perfect."  Despite this obvious truth, there is another realization that must be taken into very serious consideration.  It is always best to have another set of highly trained ears on any given project at some stage in its development.  These are words I live by and tell all my clients.  Its a critical element.  I will gladly Master a project that I never had anything to do with up until that point.  I will NOT Master a project in which I played all other professional roles of production services.  To say it simply, another set of skilled ears will definitely hear things differently from me and hopefully that will lead to finding things I missed, or could have done better had I heard it his/her way.  Lets face it, no matter how good I may be or become, I will never be a perfect record producer.  Truth be told, everything is an ongoing learning experience... at least from a personal standpoint.  I hope you can see it that way as well. It makes life more enjoyable when you never have a brick wall stopping you from moving forward.  Avoid the brick wall by having another set of ears on your project at some point in its development.