I'm not convinced that that was the intended message, getting another chance at better life, who knows what happens / what the tide brings. Because he literally gets it - the package he decides not to open - and doesn't use it. Yes, he "uses" it later, but he couldn't have known whether it's better for him to use it immediately, later, or never.

It's all just random decisions and luck; he could have decided to open all packages, or not open three or five of them instead of one. It doesn't mean anything.

If there is a message, then I guess it's something like that one should try to be clever and find solutions, like Mark Watney. And everyone makes errors and bad decisions occasionally.