English idiomatic proverb that expresses "work makes the doer"?

Solution 1:

"Making makes the maker" is similarly alliterated if less general, and it and variants occur a few times on the web:

• "Making makes makers" https://www.theupcycler.org/

• "How making makes the maker" http://www.redoakleaves.com/writing.html

• "As the maker makes the made, the making makes the maker" from At Swim-Two-Birds https://www.tapatalk.com/groups/thefictionalwoods/great-epigraphs-t897-s10.html

Solution 2:

Probably the following saying comes close to yours:

practice makes perfect:

said to encourage someone to continue to do something many times, so that they will learn to do it very well.

(Cambridge Dictionary )

Solution 3:

Perhaps Work maketh the man. I don't have a reference for this, but I did find references to similar expressions:

Careers maketh the man.

Habits maketh the man.

Clothes maketh the man.

Manners maketh the man.

To my mind, Work maketh the man preserves the sense and intent of the OP's rendering of the Latvian proverb, the key being the replacement of the doer by the man. Implicit in this replacement is that the man and the doer are one and the same.