What is the ruling on saying phrases such as: "My life, my soul, my heart, you are my life, you are my soul, you are my heart" to others?

It is permissible to use phrases such as "my life" (ya 'umri) and "my darling" (ya hayati) between spouses, or between parents and their children, or among mahrams. However, between non-mahrams, it is prohibited because it falls under the category of submissiveness in speech, which can be a temptation for those with sickness in their hearts. Such phrases must be avoided to prevent fitnah (temptation/discord).