>>320916301
It doesn't really matter how you reject them, as long as you're not rude or dismissive. Most people can't handle being just friends with someone they have feelings for, even the ones who think they can before they try it. A lot of people do it trying to be nice and end up miserable.
Time apart might help, or it might not, but there's no better way to go about it.
There are exceptions, but it's all up to them, not you.