In many areas of life, people systematically mispredict the emotional responses of others. In this paper, we investigate whether these so-called 'empathetic forecasting errors' arise in relation to observing and discussing counter-normative pro-environmental behaviours (PEBs) and their implications for people's willingness to engage in and talk about pro-environemntal action. In study 1, we use vegetarian meal requests as a case study and then extend our investigation to look at 10 impactful pro-environmental actions. In our first study, we use an experimental vignette approach to investigate the phenomenon in a representative sample of UK meat eaters (n=1164) and a booster sample of vegetarians and meat reducers (n=444). Our results indicate that vegetarians and meat restrictors forecast that their vegetarian meal requests across a range of social settings (a pub, a dinner party, a BBQ and a restaurant) will elicit less positive and more negative emotions than meat eaters themselves predict they would feel. In our second study, in a representative sample of the UK's population (n=1,000), we then investigate whether these errors occur in relation to 10 impactful PEBs and where they do their links to people's willingness to engage in and talk about PEB, finding mixed evidence. Taken together, the findings identify areas where empathetic errors crop up in sustainable lifestyle shifts and highlight the need for behavioural interventions to update people's forecasts.