Reincarnation may be difficult for some to believe in because it makes each individual not only responsible for their own actions, but also because of karmic circles. Simply put, (and to steal a quote from the Bible) karma can be defined as 'an eye for an eye'. In other words, if you hurt me in this life, I'll hurt you the same way in the next, so that you have to experience how it feels to be on the receiving end of the hurt. This leads to another hurdle, which is the assumption that if there are karmic cycles, then we have no control and so have to live each life entirely at the mercy of fate.
From the moment of birth the foundations are being built for the lifetime and life lessons that await. Even though the personality is already defined, the physical environment and various human interactions will also contribute to round out the overall being.
Although the new incarnation was thoroughly discussed among the participants and certain events were decided prior to birth, the entity and those who interact with it are not doomed to play out a rigid lifetime that is totally dictated by fate. To the contrary, everyone has free will and can at any time change, alter or terminate the original plan.
What this means to you is that you are not at the mercy of some sinister plan that you can't remember forming and no longer want to participate in. You have choices now and you always will. Believing in reincarnation doesn't mean that you're locked into a lifetime drama where the play is already written and you simply recite your lines and take whatever the author has written into your part. Yes, there are karmic implications to the reincarnational cycle, but there is no rush to learn everything in this one lifetime. You may begin to journey down one path as planned and then decide that's not what you wish to do after all. Someone in your karmic circle may choose not to complete the entire cycle you had originally planned. It's ok if that happens, there will be other lives and other opportunities to complete the circle.