How do I not get too attached to my friend with benefits?

I've been talking to this guy for a few weeks now. We're attracted to each other but we're just fwb. He told me he wanted to be good friends(w/benefits)& go from there. I got divorced last month. He says I need to come out of my shell & to live a little since my divorce b/c I had fallen into a routine while married. I'm pretty sure that he isn't looking for a relationship...I've sort of picked up on that b/c he says he doesn't know if this will be a long term thing or if we will end up being just friends. My ex was the only man I'd ever slept w/...until yesterday. He on the other hand has had many. I need to know how to not get to where I feel attached to this guy or that I'm falling for him. I've never slept w/a guy that just wanted to be my friend. He wants me to start opening up & talking more but I feel like that will bring me to feeling even closer to him. How can I keep myself from falling for him?