It's not a matter of "holding out" but "seeking out".
One has to be proactive about the things they want out of life.
We live on a planet that is inhabited by almost 7 Billion people.
There are lots of "the right ones" who have all of the traits you could want in a mate.
The concept of "the one" is based upon our reflex to (exclude) rather than (include) when it comes to love.
For example if a person stated "their one" has to be (a member of their own race) that automatically eliminates Billions of people right there! If you went on to say he/she must have the same relgious belief that will cut down your options by billions more.
We then say "the one" must reside in our own state or town. All this is before we get to height, weight, age, occupation, education, hobbies/interest, and goals....etc Last but not least your family and friends MUST also like him/her and vice versa!
Is it any wonder that by the time we get done EXCLUDING people there is ONLY one "right one" left! I believe once we decide what is "really important" with regard to traits in a person we'd want to spend our lives with then we are likely to find "the one" sooner rather than later. Being realistic and becoming more mature makes all the difference in the world.