The consistency paradox

Consistency is something I find appealing in a person.
In general, I think consistency in other aspects of life can be dangerous or at least counter productive.
If you're careful you become too comfortable and then resistant to change. Especially when there are areas that need a change, or at least a shake up.
A friend of mine made a comment to me last week, and it wasn't the first time he's said it, that there is a lot of same-ness in my life and it would do me good to change things.
In a way this is very wise. For me, the most important change would be if I can mentally toughen up and resist the negative and worrisome thoughts that come along now and then.
Mental exercise is a lot harder than physical exercise because it is so easy to let a thought run away with you.
As much as physical fitness appeals to me, and I'm not overly good at that, I reckon mental fitness is far more important. That's not to say you shouldn't practice both, because you should and I definitely should.