Evangelism and friendship, procreation and romance: an analogy

I am reading Marriage: Sex in the service of God at the moment. In it there is a reflection on the tension between marriage as a place of relational intimacy and as the proper place for having kids.

How do the two relate? Must we be thinking about conceiving every time we have sex? Doesn't this reduce marriage and sex to mere functionality?

The important thing, Christopher Ash writes, is that we realise that we are dealing not merely with function but also with being. People are deeply personal. Child bearing is deeply personal. We cannot melt one purpose into the other.

Now that has a lot of relevance to the way we think about loving people and being good friends and at the same time seeking that people be saved.

We cannot make friends in order to evangelise, nor can we evangelise without seeking to be friendly. We must not melt one into the other.