This has never worked for me. The extra push is exhausting, and then I use that as an excuse to skip the next day, and eventually the habit breaks.
Don't overexert yourself, do only the amount that feels good and keep it easy so that you're not turned off when you need to do it again the next day.
Once you've built up a habit, you can slowly ramp it up, but trying to go too fast has always caused me to stop altogether. If you go slowly enough that you don't notice the additional exertion, you're much more likely to keep your habit.
Contrary to popular soundbytes, you actually can improve without pushing yourself too hard. It's weird going from barely being able to run half a mile to running five miles without getting seriously winded, but it does work, and you don't ever need to feel winded in the process. If you start to feel bad, stop. Don't beat yourself up if you didn't get as far as you did yesterday, just do it again tomorrow.
I was only ever able to do this slowly. Overexerting myself always failed.
As for fun... Eh. I've gotten to the point where I feel restless if I haven't gone running, so then I go run and shower, and then I feel great. But the restless itching feeling is the habit that makes me want to go, not fun in the moment. Maybe running is weird.