Hi, welcome.
Are you using other entertainment to distract you during the rides? Until you’re used to the harder longer intervals, try and pick a less intrusive kind of entertainment. I tend to only watch stuff for lower intensity rides and then it’s music as the intensity picks up.
If you’re new to using a smart trainer and are using it in erg mode, check out these helpful resources from @mcneese.chad : Erg mode problems.Anyone had this? - #2 by mcneese.chad
Lots of the workouts have workout text that will take you through the intervals, so turn those on if you haven’t already.
And finally, some of it just comes with time. Practice, practice, practice.
Good luck!