This sentence usually appears in literature or romantic love novels to express a person's expectations and promises for the future. The meaning of this sentence can be interpreted in many ways, but the most common one is to express that a person wants to focus only on the other person in their future life and to live their life with the other person. This could also imply that one person's love and commitment to another person could be spent together for the rest of their lives in love with each other. In addition, this sentence can also express a person's wish to live a true and free life, no longer bound by traditional social norms, but to pursue their own dreams and interests. They hoped that they only had each other in their lives, but they also hoped that they could keep in touch with each other and pursue their interests. So the exact meaning of this sentence depends on the context and situation, but it usually express an affectionate promise and hope for the future.