Read it through once

“For the distinguished favour you mean to confer on me” [a present of a landscape painted by himself], “I cannot sufficiently thank you. Highly valuable it will doubtless be in itself, and I shall consider it inestimable as a proof of your good opinion. Indeed, Sir William, your praise has made me very vain. It is impossible not to be elated by such approbation, however little I may have deserved it.