what does double-mindedness have to do with anxiety and suffering?

Ever noticed how the same idea pops up in different places? You get the nagging feeling someone is tapping you on the shoulder, trying to get your attention.

Recently for me it's been double-mindedness. I didn't know it had anything to do with anxiety. Although Matthew 6:19-34 might have given me a clue. Ed Welch says,

Whose kingdom are you seeking? Do you trust the King who is also your Father? ...The real issue behind worry is that of spiritual allegiance. 

Our answer? "Sort of...a little...usually." We sort of want the kingdom, and we sort of want to trust the King - until life gets precarious.

When everything is going well and the storehouses are full, we trust him. But when there is nothing for tomorrow, we panic and track down the address of another god who can give us enough for tomorrow and the next day too. ...

Whom do I trust? Where is my faith? ... All of us already know the answer. Our trust is divided. We don't put all our eggs in one basket - even God's - because that's too risky. Our trust might not pay off in the way we hope.

We are reluctant to simply say to our Father, "I am yours," and stop worrying. ...Fear and worry reveal that our faith is indeed small ...

You trust God for some things and not others. You trust him for heaven but not for earth.

And as if that wasn't enough, here's Paul Grimmond on double-mindedness and suffering.

I remember talking a number of years ago to a young medical student who was thinking about the possibility of missionary service.

As we talked, he was refreshingly (if sadly) honest: "I know God's glory matters. I know people need to hear about Jesus Christ. I know my own comfort isn't everything.

"But what if it's all a lie? What if Christ didn't really die? What if God isn't really there? I'd have given up everything for nothing."

I think he said what many of us harbour in our hearts but are fearful to say. We are secretly worried the world might be right. ...

We live with a foot in both camps, afraid to leave Christ behind but terrified of what might happen if we wholeheartedly planted both feet at the foot of the cross. ...

It is only as the things of this world are dimmed by the glory of God that we will be able to live and to suffer for Christ [and, it seems, trust him.]

From Ed Welch Running Scared 109 and Paul Grimmond Suffering Well 149-150, emphasis mine.