If we are praying as this verse commands, our prayers might cost the ones for whom we pray more than we expect. When we begin to intercede in prayer for others, God begins to lift them into a totally
different sphere, a process that may involve trials and difficulties. We have to make sure that our natural sympathy doesn’t get in God’s way. If we slip from identifying with his interests in others into personal sympathy for them, our vital connection with God will be lost. Putting sympathy first is a rebuke to him.

It is impossible to pray vitally unless we have perfect confidence in God. Personal sympathy and prejudice weaken this confidence; identification with God ensures it. Whenever we stop being identified with God, it is because of sympathy, not sin. Sin isn’t likely to interfere with our relationship to God, but sympathy will make us say, “I refuse to allow this to happen.” When we refuse to allow God to have his way, we have lost our vital connection with him.

If we are interceding properly, we have neither time nor inclination to pray for our own sad, sweet selves. It’s not that we’re working hard to keep thoughts of ourselves at bay; thoughts of ourselves simply aren’t there. In vital intercession, we are completely and entirely identified with God’s interests, and our natural sympathy—for ourselves and for others—is entirely eclipsed.

Wisdom from Oswald

Sincerity means that the appearance and the reality are exactly the same.
Studies in the Sermon on the Mount