I’d also look at your actual riding outdoors first if every single ride is hard. What’s the terrain like, lots of hills? How’s your gearing? Hilly areas with tall gearing can be really discouraging for new riders, and many new bikes don’t come with low enough gearing for new riders.
You may want to take your bike to your local shop to sée if they can set you up with lower gears since you need to be able to do easy rides as well as hard rides. Then just start going out a few times a week, increasing ride length and frequency over time. And make sure you finish at least a few of your rides a week feeling like you could’ve gone harder.