Training to me has a lot of parallels to JRPGs:

While we would normally play a JRPG for the story and enjoyment, we would train for VASTLY different reasons:

Each of these things tend to create a singular focus, which we don't really notice at first because we're fixated on a goal. For weight loss, or any of these, we may see some early results. Weight may come off, blood pressure may drop, but eventually that progress will slow. This begins what I like to consider the first parallel with JRPGS:

Just like in any JRPG (Final Fantasy etc) you inevitably get to a boss that completely pwns you. In these games, it's time to go kill things over and over and over again until we raise our level, and then try it again. Hopefully not getting pwned this time.

Even JRPGs realize that "holy crap, people actually paid for this so it has to be kind of fun". In order to facilitate what we call pacing in that industry, side quests are introduced to take your mind off of how painfully dull whatever you were doing was

The fact is these are all deviations in focus. The goal is to make you focus on something in the near term, something more immediately achievable, while driving you in the direction you need to be going.

In Fitness, I like to refer to these as moving targets. I like to think of my goal as being made up of 30 / 40 smaller goals with their own metric:

When weight began to slow down, I embarked on varying side quests dealing with each of these other measurements. Week-by-week, or day by day in some cases I would set a goal for each one and keep moving along that way. You'll find that over time what was your original goal metric will begin moving again as summation of all of the work you've done to hit your moving targets

Make Side Quests For Yourself

JRPGs are also fantastic at throwing in completely self-contained games in which we can lose hours and hours of time. Gwent in the Witcher III, Blitzball in FF X. While they're tangential to the whole experience, the point is they keep you engaged.

In a parallel with fitness, I see Mini-Games as cross training. Find things you can do that are NOT DIRECTLY RELATED to your primary discipline and start working on them. You'll find that you can quite possibly become just as absorbed in that discipline as you were your first.

It leads into its own rabbit hole of moving goals and side quests for cross-training goals, but you'll find that you're never bored with working out. There's always something else to do