I think most habits us highly effective language learners have are that we're dogged, persistent, self-confident pieces of work that don't take anything for granted and work hard to get where we are. We've got a source of motivation that doesn't run dry (I think I am one of those people that thinks that if I have to work up the motivation to do something, I should be doing something else, unless it's basic survival stuff). There are specific routines I would recommend, but since routines vary and everyone's different I always think that I need to work with a person individually before I can comment on what would likely benefit that person. (And I get paid to do that job, so...)
I honestly don't care what other people think anymore about what my levels are like and whether my Czech is a B1.3 or a B2.778 or a C4 explosive. (It's obviously the last one). I speak loads of languages at mediocre levels and they've still been useful. I think I tend to get further in my slightly Dutch-accented, grammatically obnoxious German than some people who have spent their lives analysing Goethe. My habit is that I just use German when I need it, whenever that happens to be, and that I do it with the confidence that I can manage things in German however horrible things may turn out to be.
I like to think that most polyglots I know are effective, have fun with their languages, and manage very well. I, personally, though, will make a point of only presenting at Gatherings/Conferences in non-English tongues from now on, just because as a polyglot I find that more fun. Most of those people I know (and they're not necessarily the ones with the most media attention) are effective because they know what they want, why they want it, and go for it no holds barred.
Diaries left with cryptic entries
Preferred pronouns: feminine.