Ask any fit or sporty individual you know. They don't do it because they have to. They do it because they want to.
The boredom you mentioned is natural. Everybody gets it at the exact same strength and at the exact same moments. The difference is that some people are disciplined enough to continue and burn through it. And only then you get to see the fun and enjoyment part.
Discipline is king. With anything else you're just lying to yourself. Nobody will create the perfect environment for you to be comfortable with physical effort. You're the one that has to do it.
You know how I know you're full of it? Its the bullshitter's law: the amount of knowledge a person has is inversely related to how well they claim to know a topic.
Since you already know everything about motivation and achievement, there's nothing for me to discuss here with you. Everyone is weak and stupid except for you.
What's more important is finding activities that are naturally motivating and fun to do. These habits are far easier to build when they are more rewarding.
And then you naturally build discipline because the cost of missing out becomes more expensive to you.
What's more important is finding activities that are naturally motivating and fun to do. These habits are far easier to build when they are more rewarding. Rock climbing, squash, swimming, martial arts. If its fun, then you WANT to go more often. You actually think about improving your skills. And then you naturally build discipline because the cost of missing out becomes more expensive to you.