Mindfulness has transdiagnostic applicability, but little is known about how people first begin to practice mindfulness and what sustains practice in the long term. The aim of the present research was to explore the experiences of a large sample of people practicing mindfulness, including difficulties with practice and associations between formal and informal mindfulness practice and wellbeing. In this cross-sectional study, 218 participants who were practicing mindfulness or had practiced in the past completed an online survey about how they first began to practice mindfulness, difficulties and supportive factors for continuing to practice, current wellbeing, and psychological flexibility. Participants had practiced mindfulness from under a year up to 43 years. There was no significant difference in the frequency of formal mindfulness practice between those who had attended a face-to-face taught course and those who had not. Common difficulties included finding time to practice formally and falling asleep during formal practice. Content analysis revealed “practical resources,” “time/routine,” “support from others,” and “attitudes and beliefs,” which were supportive factors for maintaining mindfulness practice. Informal mindfulness practice was related to positive wellbeing and psychological flexibility. Frequency (but not duration) of formal mindfulness practice was associated with positive wellbeing; however, neither frequency nor duration of formal mindfulness practice was significantly associated with psychological flexibility. Mindfulness teachers will be able to use the present findings to further support their students by reminding them of the benefits as well as normalising some of the challenges of mindfulness practice including falling asleep.Electronic supplementary materialThe online version of this article (10.1007/s12671-018-0951-y) contains supplementary material, which is available to authorized users.