Hare Krsna devotee, Manu samhita and some puranas deal with this subject. It depends on what is your varna. If you are a sudra ,vaishya , Kshatriya or brahmin. Also who the promise was too and for what. Then there is the consideration of why the promise was broken and was there an emergency or a life threatening situation. So many things are to be considered. In certain situations breaking a promise may even be praise worthy. But generally someone who does not keep there promise is considered a cheater. Then how big a cheater are they. One who claims to be god and promises heaven for their followers to collect money and servants goes to hell and their followers go with them. In that hell they suffer greatly and the followers give repeated torture to their so called savior. we take shelter of Krsna who is glorified in all the Vedas as the Supreme Personality of Godhead. He is the infallible Lord Achyuta and he promises to protect His devotees from all sinful reactions. Do not fear. .