Using email for conversations means you often have to go back to earlier messages to see what you said. That can be a chore, unless you have conversation view turned on.
In Gmail, there’s an easy way to turn this on. Head to the gears icon in the top-right corner of the screen, and then click the “settings” option.
Then, a few options down you should see the choice to turn conversation view either on or off. It should be left on by default, but if you need it on or off you can always go back and change it.