C'mon, I mean really. I can't emphasize enough the joy and liberation purchasing a lifetime treasure can bring you. This isn't something disposable. You're purchasing a legacy. Something that will remind your descendants of who you were.
Art only goes up in value, never down.
This is not only a financial investment, but an investment in yourself. Its worth is measured in the eye of the beholder as well as the wallet. You should never feel guilty for occasionally feeding your heart and soul. If a piece of art can bring you continued joy, day after day, then it has become a necessity. Taking without asking is stealing, no matter what.