A recent study has found that mindfulness can impair implicit learning. It makes intuitve sense that being more aware of oneself means one is less likely to develop bad habits, since self-monitoring should (in theory) help to staunch behaviours before they form into habits (i.e. before they become routine).
However, there are two further implications worth considering, which are perhaps less obvious. The first is that mindfulness can also inhibit the formation of beneficial habits. The second is that habit-forming (of whatever kind) is not typically considered to be "learning" insofar as 'learn' is commonly associated with effort rather than passive reception. This study might suggest mindfulness itself requires effort. It certainly raises questions about the potentially detrimental results of expending such effort.