Louvre blues? The antidote is Musee Jacquemart-Andre (B Haussmann, west of Gare St Lazare).
Climb the lightest of monumental staircases to a wonderful private art collection in a sumptuous Second Empire mansion. Splendid audioguide.
And when exhilarated rather than exhausted make for the tearoom, or walk back along Boulevard Haussmann for celebratory lunch at Brasserie Mollard.