How do I remove the last word after 1 click?

I am creating a project to practice remembering words in which each time a forward button is clicked an extra word is displayed in the text box but each time a "back" button is clicked a word is removed from the textbox,

Problem- Each time I am clicking the back button a word is not being removed from the textbox and I had tried to get my computer count the number of characters in the last token and then remove those characters from the text but this is not working.

What I want to do- Given the text in a variable with only on word showing in my textbox I want that whenever I click the forward button one word be added to the textbox and whenever I click "Back" one word should be removed from the textbox with those words being extracted from the text in my variable sequentially.

And below is the link for the file

dropbox.com/s/fxa3bmmoptdk447/Deliberate%20Practice%20with%20Text.c3p

And I think that it will be good for practicing the word by word memorization of text,

And,

Have a Great Day.

Here's how I would do it.

dropbox.com/s/9xhlm4zkf2411oa/Deliberate%20Practice%20with%20Text.c3p

Thank You.