`cancel_timer(State, #state.field_to_change, Msg)`

```
cancel_timer(Rec, Num, Msg) ->
    Ref = element(Num, Rec),
    cancel_timer(Ref),
    ...
    setelement(Num, Rec, NewRef)
```
Or something like that.

That being said, I prefer operating on values rather than having a monster like that :B