‘But I say to the unmarried and to widows, it is good for them if they remain even as I. But if they do not have the ability to control their desires, let them marry. For it is better to marry than to go on burning with unrequited desire (literally ‘than to burn').'
Paul is saying here that the unmarried and widows will do well if they remain in that state just as Paul is. There is nothing wrong with it. It is not contrary to God's commands. And there are certain benefits, which he will shortly point out, which, all other things being equal (which sexually they rarely are) favour celibacy. There is no sin in remaining unmarried for those so gifted that they will not be excessively tempted by it. It is ‘good' (just as marriage was recognised as being ‘good').
Elsewhere, however, Paul makes clear that this advice is dependent on what gift a person has. He recommends younger widows to marry (1 Timothy 5:14). He had come to recognise that they were not necessarily good judges of their own self-control. He recognised that celibacy was not to be recommended for the majority of younger people. But he would still have accepted that there were exceptions to the rule.
But those who do not have the self-control which enables them to abstain from sex without undue temptation should marry. That is their gift from a gracious God. It is better than having to constantly fight the sexual urge (present tense) or give way to it illicitly. Constant committing of adultery in the mind would be far more harmful, and far more of a hindrance to their Christian lives, than being married. We must not be ashamed to admit to weakness. All men and women have weaknesses. Thus we must cater for them as seems fit. (Many find such obedience difficult even when they are married. But marriage prevents such desires from becoming uncontrollable).