I like the thought I heard from one speaker, that love is more of a complementary than a supplementary thing.
You should never say that someone completes you. Cause you don’t find someone to supplement the longing that you have. For needing a certain someone is not love but dependency. You need to feel whole even you're by yourself, cause if you are not happy being alone, you’ll never be complete having someone who is also unhappy. Making the scenario worse... imagine two unhappy individual finding happiness from each other.
This may sounds fair or unfair to you. But for me love is a union of two complete individuals that complements one another - know who they are… content with themselves… So search not for someone who will complete you, but for someone who will complement your completeness.