I have a lot of friends that refuse to believe in pickup. No matter how much success they may see from me, they just don't think they can do it.
That said, most of them have eventually found partners. Think of all of the AFC's in this world that have wives. Sometimes life connects them. Your friend may fall into this mold.
We have a section in our book where Ma$e goes through a period kind of like what you describe. He stops dating all together and reinvents himself. When he gets back out there, he is more powerful than ever.
So how does that apply? Invite your friend out to social activities. Grill N Chills. Game Nights. A baseball game. Get a bunch of people together, including women you'd be ok with him meeting. As he gets involved with this group and realizes it's fun, he may be more inclined to come out with you in the future. Then when you disappear and pull a two set back to him, he will help with decent conversation and may become more interested in pickup.
If anything, you can know you've tried and focus on other friends. We can't save them all.
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