This manuscript proposes a novel theoretical mechanism for how and why people adopt goals. In Study 1, participants exhibited increased adoption of a target goal (self-reported importance of close relationship maintenance) when a salient attainment means for this goal (writing a personal email to a loved one) had been associated with positive affect. Because this goal-adoption effect could not be explained by elevated mood, we concluded that increased goal adoption was due to transference of positive affect from the attainment means to the goal. In Study 2, we aimed to moderate this effect, predicting that means-to-goal transference of positive affect (and hence increased goal adoption) would only occur for participants that strongly associated the attainment means (writing an email) with the goal (close relationship maintenance). To test this, some participants wrote an email to a loved one, while others wrote an email to an acquaintance. Another goal of Study 2 was to test whether positive affect can transfer up to a goal and then back down to an alternative attainment means: giving (vs. keeping) a gift to a loved one. Analyses indicated that the introduction of this additional, alternative attainment means resulted in goal shielding (different attainment means for the same goal inhibit one another). Consequently, participants that had written the positive email to a loved one were actually less likely to give (vs. keep) the gift. Ultimately, Study 1 provides key evidence for a novel theoretical mechanism for goal adoption. Additionally, Study 2 provided key insight regarding the boundary conditions for affective transference within goal systems. Altogether, the current research provides important theoretical insight regarding goal systems theory, and it offers practical applications to education, business management, and public policy.