"U" stands for "UPRIGHT". The Oxford Advanced Dictionary defines the word "upright" as 'behaving in a moral and honest way'. Based on this, when you profess to love someone, how upright are you towards him/her?
Do you say you love and yet, cheat on your partner?,Pressure or seduce them into sleeping with you when you know that your body is the temple of God?, Use tricks and lies to drain them of their hard-earned money? How up to standard are your moral ethics and honesty or do you see them as outdated?
If Christ hadn't been upright, maybe we would have an excuse but our Lord was upright and honest and as his disciples we are called to do likewise. So when you want to utter those words - I Love You, make sure you are ready to abide by all it entails because on the last day, we would be held accountable for each word we utter.
Finally, we need to ask God to really help our heart to love others as He loves us so that when we utter those words, people would really see it in our actions and not only our words.
May God help us all to live and love like Him in Jesus' priceless name, amen!