You really wanted someone's approval. Your past and your unstable feelings were not to blame. You admitted it at a certain point, you are to blame for your own actions, all out of love. All that drove you to commit genocide was love for that someone.

It didn't take long for L to realize this, so he decided to take advantage of it. He got you out of prison temporarily, in exchange, he would offer you to join Kira's case. "Once this is over, I promise to reduce your sentence by 3 years less."