I've got 5 types of coffee in the house right now (one Colombian, one Peruvian, one New Guinean, one Ethiopian, one unknown blend).
All coffee shares the same fundamental taste, but the variations in strength, of the aftertaste, of the aroma, of the color, etc ... all make each batch of coffee slightly different from the last.
On top of that, each coffee tastes different once you add another compound to it -- a coffee with cream is distinct from a coffee with butter, is distinct from a coffee with coconut milk.
The reason for bringing this up is that we tend to derive a lot of happiness from small deviations from what we expect. This then becomes a starting point for effortless sustainability.
It is particular useful when we're trying to make a habit change. We all know that changing habits is difficult if approached with the mentality of deprivation -- "I no longer get to do X". Rather, the most efficient approach is to introduce a new habit -- "I'm the guy who gets up in the morning to run, bike, or swim".
Applying the same principle of having multiple variations which are proximal in your mental heuristics tree is potentially a strategy that can pay off -- variations bring with them proximal rules of thumb that make it easy to derive a novel stimulus to the brain, that wires it up to expect success and excitement.
eg: slightly different workouts to challenge the body without losing the intended primary stimulus.
ie: when in doubt, more shades of the same.
The mantra "No Pain. No Gain", is a flawed belief.
Firstly, it assumes that you are the centre of the world; that the outcome is contingent on how much effort you put in. (when oftentimes, success is pushing through strategic pieces, and letting nature and chance lead the charge)
Secondly, that attitude is devoid of all respect for oneself; doing so will expose oneself to serious chronic injury.
Instead, the mentality should be: I need to do what I need to do, and need to deliver the required results. I can push through pain. I can't fight through injury.
You are your own boss (and if you're not, start fixing your life). Expectations are malleable.
I'm pretty confident that the moment people give themselves a hospitable mindset to pursue their goals, they will adopt the mentality that pain is to be expected ... not deserved, not earned. It just is. It's just there. Say hello.
The keyword is "hospitable". Hospitable isn't "comfortable". It isn't "painful". It's "enlivening" -- promoting life.
And that's a long way of saying, just do what you fucking need to do. And stay safe.