There are so many books that simply focus on the idea of a person having a "one true love".  Most books that focus on this topic involve a girl stuck between two guys.  I think that, as romantic as the idea is and sounds, it's completely cliche and totally not something you should hold your breath for to find find.  Here are my reasons why:
  

In Twilight, Bella Swan was caught between Edward, her mysterious vampire boyfriend who's too dangerous for her human self, and Jacob, her werewolf best friend who is absolutely in love with her.  Bella Swan is a plain human girl who moves in with her dad who lives Forks.  There, she meets Edward, a mysterious yet strangely beautiful guy at school who seems to have an objection to blood.  As the series continues, Bella falls in love with Edward, who leaves her, saying that it's too dangerous for her to be with him.  Well that's when Jacob swoops in and makes her trust him.  Jacob falls in love with her and practically "imprints" on her, yet when Edward returns Bella falls back into his arms.  She plays the damsel in distress card, she acts innocent, miserable without Edward yet miserable without Jacob as well, and yet, she's a self centered human girl.  In the end it turns out her daughter, Renesme, is Jacob's true love, a child who looks like her and has her blood, yet isn't her.  His second chance.  Yet even there, for a long time, Bella was caught between two guys while they forced her to make up her mind about which one she loves more.  Fans create "Team Jacob" and "Team Edward" in order to show who they would choose. 
  

In another vampire story, there's Elena Gilbert who meets and falls in love with Stefan Salvatore, who, it turns out, she's destined to fall in love with because she's a doppelganger and so is he and the doppelgangers are supposedly "destined" by "fate" to fall in love because of some witch.  Stefan is on a sort of "diet", similar to Edward Cullen and his animals only diet, making it possible to withstand being with Elena.  His older brother however, Damon, is not on a diet, yet he has no trouble being around her.  Damon loves trouble and causing it, and yet, even though he does all these things to make Elena and Stefan hate him, she falls in love with him in the end and choose him.  This story has the same idea, two good looking, yet completely dangerous guys who go after the beautiful human girl who's completely helpless.  In both stories the girl turns into a vampire, in Twilight it was on purpose, in The Vampire Diaries it was on accident, but for a good reason.  Still, Stefan believes that Elena is his "one true love" and maybe she is, yet she loves Damon, and she can't be happy if Damon isn't happy, yet she can't be happy if Stefan isn't happy.  She's caught in a love triangle, yet she's capable of being with one while the other is miserable. 
 

  In The Hunger Games, Katniss goes to the Games and finds out that her fellow tribute from District 12 is in love with her, and that he has been for a long time, and then, once she returns from the game, with Peeta, the boy with the bread, as her "lover".  After she returns, she finds out that Gale, her best friend and hunter, is in love with her and hates her relationship with Peeta.  Especially since she cares about Peeta and becomes engaged to him.  Every time Katniss has a problem with Peeta, she goes to Gale.  Every time she's hurt, she goes to Gale, which isn't fair to him, yet he can't resist her because he's in love with her.  Katniss is in the same position as Bella Swan and Elena Gilbert, she falls in love with one, yet she loves the other too much to let him go.  Though Katniss is far from weak, she is a needy, self-centered girl much like Elena and Bella.  Bella plays the "I'm only human" card way too many times, Elena struggles with her humanity, and Katniss pushes everyone away because she thinks that that's what she needs to do in order to survive.  She becomes almost barbaric and inhuman with her actions and survival tactics. 
  

In ABC Family's TV show, The Lying Game, Emma Becker is caught between Ethan Whitehorse, and Thayer Rybak.  Her twin sister, a sister who she never knew about for most of her life and who had a perfect life, was in love with Ethan Whitehorse, that is, until Sutton decided to go off and leave Emma in her place, impersonating her.  Ethan fell in love with Emma, who was pretending to be Sutton, and when he found out, he fell even more in love with Emma.  Well, like our other stories, Emma leaves Ethan for Thayer, yet somewhere deep down she still loves Ethan, even though she's in love with Thayer as well.  Similar to The Vampire Diaries, Sutton is like Katherine, in love with Ethan (or in Katherine's case Stefan), yet Ethan (Stefan) is in love with the look alike (doppelganger/twin). 
  

My last example has a good ending.  In Cassandra Clare's series The Infernal Devices, Theresa (Tessa) Gray falls in love with two parabati brothers, William (Will) Herondale and James (Jem) Carstairs.  The nice part of this story, though Tessa falls in love with Will first, and then later Tessa, Tessa gets to live her life with both of them when Jem dies and goes on to be a Silent Brother, leaving the two most important people he loves together to live happily ever after.... of course except for the fact that Shadowhunters don't live forever and Warlocks do.  A hundred years later, long after Will died, Jem is cured and has the choice to live his life out with Tessa, a still young Tessa, and she gets to have both of them, without having to choose which one to have and which one to break. 

So there is my opinion on the "One True Love" factor.  As much as I love reading stories with love triangles like that, as much as I enjoy the teenage dramas involving them, I will say that they are cliche and a little overrated.  Especially the girl who usually, not always, but usually, plays the "damsel in distress" card.  I enjoy the books that have the love triangles, but honestly, don't write a story with a love triangle and the idea of the "one true love" if you're going to make the girl whiny and in distress.  The idea of someone having a "one true love" and "fate" bringing them together is entirely cliche and, though it may be possible, I wouldn't be broken up over someone if they leave you and you think that they were your "one true love".