In response to the call for elucidating the catalyst of consumer citizenship behavior in micro-entrepreneurship, this study explores the determinants of “sharing citizenship behavior” (SCB) within the peer-to-peer (P2P) accommodation environment from the host perspective. Particularly, it emphasizes the role of well-being (encompassing both the hedonic and eudaimonic forms) and the influence of “trait gratitude” (TG), all within the framework of the broaden-and-build theory. This research explains the mediating effects of both hedonic well-being and eudaimonic well-being (EWB), revealing multiple positive correlations among TG, well-being, and the SCB of guests. It also uncovers the moderating role of price fairness on the link between TG and EWB. It provides valuable insights for P2P accommodation micro-entrepreneurs on the SCB and the well-being of their guests.