The structure and predictability benefit
A consistent routine provides a reliable anchor point in an otherwise unpredictable life, which can genuinely support a sense of stability and control, particularly during stressful periods.
The mastery and accomplishment benefit
Regularly setting and achieving small fitness goals — a slightly heavier lift, a longer run — builds a genuine sense of competence and accomplishment that contributes positively to overall self-esteem.
The identity-building benefit
Over time, consistent training can become part of someone's genuine self-concept ('I'm someone who exercises regularly'), which tends to support continued motivation beyond relying purely on discipline or willpower.
Why this benefit depends on the approach being genuinely sustainable
These psychological benefits depend on the routine being approached in a healthy, sustainable way — an approach built on rigid perfectionism or excessive self-criticism can undermine, rather than support, these potential mental health benefits.