If you could paint than I can walk

He was always a painter, but he stopped painting when he was younger. After her met her, he revived his love of painting and became successful with them. Irene Dunne is saying that if Charles Boyer can get back that part of himself, she can also get back that part of herself and one day walk again.

I thought this was a little abrupt and puzzling too. I wasn't sure if the meaning was, as the other poster described, speaking of regaining that part of oneself which they had lost...or if it meant his painting would bring money for her to have the operation that she discussed with her former fiancé (when she refused to allow him to pay for it). I could have it completely wrong, though.

Boyer says repeatedly - both to be utterly candid with this woman with whom he's fallen in love - but also in some amazement as he says it "I've never worked a day in my life". He's gotten by on looks and charm - and seems virtually a gigolo. Much of the film I think is about their efforts to improve themselves - to be worthy of each other. The very reason they wait six months to meet at the top of the Empire State Building is so that he could begin a career, one by which he could himself make a living - at painting - and presumably support her if they married.

He had been a dilettante, gave up things that were difficult, required much effort - now over the six months after he disembarks, he's really going to try - so that they can have a future together. He has almost no success in New York - he winds up painting billboards - but when he returns to his grandmother's home - he finds himself and works hard - and returns with an entire gallery of paintings which sell well.

By the time they see one another - it's 1.5 years after they left the ship. He's become a painter - he can plan a future - and so she makes her remark when it's clear that their future will be together.