Of course we have an easier time of it when we can be less rigid and "controlling." It's easier to allow ourselves to be less rigid if we don't become perfectionistic about the idea.
But if we accidentally create a false choice- either we are "in 100% control of everything" or we "have no control over anything"- we will end up too scared to let go at all. If the alternative to what we've been trying to do (have 100% control) is 0% control (or, put another way, "complete chaos"), I can't imagine anyone thinking it'd be a good idea to give up any control and be less rigid.
Fortunately, there isn't a black and white situation here. There aren't only 2 choices. It's ok, and safe (and a really, really good idea) to let go of some control and rigidity. Doing so doesn't mean a dramatic slide over into chaos (and it doesn't mean getting fat either, for the record).
How, exactly to begin taking steps towards being less rigid and overly-controlled/controlling is unique to each person and where he/she is in her life and in her recovery. It's a great project to work on with a therapist or in some other structured environment and relationship/s- since it can be a bit of a nerve-wracking process, especially when someone is first learning to hold on a bit less tightly.
Of course we have an easier time of it when we can be less rigid and "controlling." It's easier to allow ourselves to be less rigid if we don't become perfectionistic about the idea.