If you do that, then when Google syncs the folders again, the source (unchanged) file will overwrite the destination (changed) file and vice versa.
When making changes to a file, rename the changed file and keep both the original file and the changed file.
E.G.
My Text File - Original.txt
My Text File - Changed.txt
Then when Google syncs the folder it will have both files stored and you wont lose either of them.
If you make further changes then name the changed file My Text File - Changed 02.txt.