Promisses are not written on stones and can be broken without any serious consequiences. However, any promiss should be appreciated withtout expectation and judgement.
Every human being is equiped with the most powerful tool for manifesting our desires - our minds hence our thoughts. You are the creater of your own reality, however, thinking of your friend as cronic liar, using words such as "hard to come by" and "don't trust" will only bring you more of hardship and untrusting people into your life.
It's about time you start believing in yourself, appreciating the body that you,have, the organs that good and be grateful to the organ not at ease for bringing you to this point in time.
Believe in your body and its ability to heal itseff, believe an organ will come your way without doubt and universe will set everything in youf favour. So I say go with flow, just remember some of the pointers mentioned above.
Hope this helps.