"When we cannot bear to be alone, it means we do not properly value the only companion we will have from birth to death -- ourselves." (Eda J. LeShan)
We humans are incurably social creatures. Our instinct to pair up is reinforced (in increasingly unhealthy ways) by the codependent mantra that 'two are always better than one' and that 'you're nobody 'til somebody loves you.' Turn on the radio and you'll find yourself serenaded into fear of being alone: "All by myself, don't wanna be all by myself!" or "I get so lonely, baby, I get so lonely I could die."
In the real world, needing someone in order to survive is not the most attractive trait. It feels desperate and weak. Strong marriages are not made of weak individuals.
So learn how to fulfill yourself on your own terms. Give yourself some much needed attention. After all, you're the only one who will be with you from birth until death. Why not learn to enjoy your own company and invest in growing and bettering yourself?