You must not have regrets after, but there's nothing to say really. The only thing you can do is offer comfort and show your love. These moments are precious and fleeting. A man that knows he's dieing has either made his peace, or is about to. Make sure you listen carefully to what he says, and try to be as comforting, gentle and understanding as you can be. This can be intense, but take comfort that he will no longer suffer and all things must pass. If there is something pressing, he will bring it up. It is his moment. The last words on his breath will not be wasted among loves ones. Good luck Bumble Bee. I know it must be difficult. My heart goes out to you.
If he looks into your eyes, they will do most of the talking. Let it flow from your souls. Nows the time to forgive any wrongs. You can do this with your eyes too. Love speaks volumes.