He likes me and I like him too but he doesn't know that cause I keep rejecting him, it hurts to see him waiting, how can I make him stop trying?

So I like this guy but I cannot be with him for a personal reasons that I don’t want to share with him, and every time I reject his offer to be with him hurts.
He is persistent and every time we talk he tells me how much it hurts for him to get rejected again and how much he wants to be with me!
Around 4 months ago he stopped trying and after 2 months his granny died so I sent him a message to give my condolences and he took that as green light signal so he started trying again and I started rejecting him again, I feel like instead of making him lose interest, I’m leading him on.
Help me out, how can I make him lost that little hope he’s hanging on to?
He likes me and I like him too but he doesn't know that cause I keep rejecting him, it hurts to see him waiting, how can I make him stop trying?
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