What's the meaning?

of steam here:

poster 1: "Thank goodness my boyfriend, who is pretty hairy, doesn't have any significant growth on his back. Shaving his legs would be a nightmare."

poster 2: "lolz if you can't stand the thought of light body hair removal with your guy, if that really is the case i doubt your relationship has the steam to make it through the real tough stuff when it happens."

I generally know what it means, but just wanna make sure and get a more precise answer.

Thanks a million!