Abstinence is OK. So is Natural Family Planning — part of that planning is abstinence.
ONLY for the very specific purpose of prayer.
1 Corinthians 7:1-5 Now concerning the matters about which you wrote: “It is good for a man not to have sexual relations with a woman.” But because of the temptation to sexual immorality, each man should have his own wife and each woman her own husband. The husband should give to his wife her conjugal rights, and likewise the wife to her husband. For the wife does not have authority over her own body, but the husband does. Likewise the husband does not have authority over his own body, but the wife does. Do not deprive one another, except perhaps by agreement for a limited time, that you may devote yourselves to prayer; but then come together again, so that Satan may not tempt you because of your lack of self-control.
It says nothing good about abstinence within a marriage, as a matter of fact, it goes against God's design for marriage and His command to husband and wife.
Nor does God allow for abstinence for the purposes of preventing conception. Birth control by any other name is still birth control.
You can dress it up as *natural* and give it the church stamp of approval, but it is still birth control.