I have an expession (it is the result of Fit) but I want to print or display an abbreviated form with all numbers in it rounded to say 6 decimal digits. 

`Print[N[polynomial, 6]]` does not what I want and ToString also has no option to limit the number of digits.

I rather get an expression with `0.0008834432170369743*d` in it (the other coefficients also have physically meaningless digits which I would like to get rid of).

**How can I transform an expression to a string limiting all numerical constants in it to some given number of relevant digits?**

I further want to use such a string for fit in a constuct like this:

> 
> 
> ```
>     Show[{ Graphics[myPlot]
>          , Graphics[{Black
>                      , Text[fit
>                            , {2, 1}
>                            , {-1, 0}
>                            ]
>                      }
>                     ]
>           }
>          ]
> 
> ```
> 
>