It is a little disappointing how few programmers know how to construct a nontrivial loop that both always terminates and does what it’s supposed to for all inputs.
Binary search is a classic example. If you think it’s trivial to get right, you probably aren’t. Knuth has some interesting things to say about it in The Art of Computer Programming.
You have to look at both. If it turns out that the body's behavior can be easily described in terms of the loop control variables (or the reverse), great, but assuming that it does and trying to fix up things when that gets complicated is a disaster.
Of course, if you dislike break, you can fake it with continue and a flag, as long as your loop control guarantees termination. However, that complicates understanding the loop's behavior in terms of said control.
I rarely write loops where the relationship between the loop control variables has anything meaningful to say about what the iterations did.