It comes as God Wills 
One thing that many Saints & spiritual writers warn against, is this: when we receive graces, and find that our bodies and our psychologies respond to these blessings (which is no surprise - for we are not souls imprisoned in bodies, but unities of body & soul together), they should never be forced. If God gives us these things, fine. If He does not - that’s just as fine. What we need to do, is love God - no matter how we feel.
So: OTOH, these good things are to be received as the gifts they are - & OTO, they can’t be relied on; because we know of joy (for instance) through its effects on us; in our intellects or in our bodies: & the chemical & general material make-up of our bodies has a way of influencing how we feel; it is changeable - and that is no basis for a life-long discipleship of Christ. We must not:
- be greedy for such graces (“consolations”, as they are called)
- or try to hang on to them
- or try making ourselves feel them
- or live our lives around them - that is like living for one’s next “fix”; they are not drugs, to deaden us; they are given to help us become truly alive & active in Christ, for His sake. Not for our own private ego-trips; flowers unfold by looking at the Sun, not by fixing their attention on themselves.
The joys we receive, are given to us so as to attract us to the God Who is the Source of all joy. Trying to hang on to them, is like hanging on to milk - its purpose is to be poured out & drunk, so that it can nourish the drinker; not to be hoarded & go rotten. So with these good things: God pours them into our hearts through the Holy Spirit so that they can strengthen us, by reminding us of the wonderfulness of the God Who is so good to us, and Whom we need to love in return. If we try to hoard them, they will “curdle” - just as the manna the Israelites tried to hoard overnight (instead of trusting in God) went rotten, and stank.
If we feel joy at the thought of good & holy things, God’s things, that is an indication that this joy is, at least in some degree, God-given. Sin can’t cause joy. If there is “unspeakable joy” in the Love of God, to reject that Love can’t be like being in it.
It is in practice not possible to “peel” apart “natural” from “supernatural” elements in joy; for it seems God deals with us by giving Divine goods by means of matter. That which is purely Divine can often not be divided from the thing that makes it available to us, without making the Divine gift inaccessible: separate Christ into “man” and “God”; & one is left with no Christ, & no salvation through Him.
So here too: if what seems to us to be Divine, truly is; we will only know by its effects in us: not by taking it to bits. For instance, do we become more peaceful, more forgiving, less self-willed, more obedient ? It is not possible always to say, “this in particular caused that in particular”; simply because we are complicated creatures: tears
may be caused by joy - or we may be more emotional than we realise
That is why a wise spiritual director is so important - those who are wise in such things can help us to be wiser than we are without them. Self-knowledge can often give us at least an approximate answer to some of our questions ##
