Let's start with the basics shall we. Proverbs 4:23 says "Keep your heart with all vigilance, for from it flow the springs of life." Proverbs 5:15-17 says "Drink water from your own cistern,
flowing water from your own well. Should your springs be scattered abroad streams of water in the streets? Let them be for yourself alone,
and not for strangers with you." The similarity between these verses is springs. Proverbs 4 describes the heart as the source of the springs of life while Proverbs 5 goes on to say drink from your own springs and don't let them be scattered. Do you see the point? Guard your heart and don't let it scatter. When you give your heart to someone and it doesn't work out and you give your heart again then you are scattering your heart. Proverbs 5 goes on to say in verses 18 and 19 "Let your fountain be blessed,
and rejoice in the wife of your youth, a lovely deer, a graceful doe. Let her breasts fill you at all times with delight; be intoxicated always in her love." If you read the whole passage from Proverbs 4-5 it's clear that what Solomon was saying is guard your heart, don't let it be scattered, and save your love for your wife. It doesn't say the girlfriend or your youth or crush but wife. The Bible gives clear direction that we are to guard our hearts and save love for those we marry after we marry them.