A person comfortable with themselves can choose relationships instead of needing them.

There is a large difference between choosing someone and needing someone, and the person on the other end can usually feel it. Comfort with yourself is what makes the first possible: you are there because you want to be, not because the alternative is unbearable, and that changes the whole quality of the relationship.

Ask of a current relationship whether you would still choose it if you were completely fine alone. If the answer is yes, that is worth saying to them. If it is unclear, the work is on your own capacity first, because it is what makes any real choosing possible.