Would you please paraphrase the following more easily?
One can have no smaller or greater mastery than mastery of oneself.
---Leonardo da Vinci
I think I'm familiar with sayings like "there's no greater mastery (or conquering) than mastery (conquering) of oneself." But the above is confusing.
Leonardo appears to be trying to present wisdom in the form of an apparent paradox.
However, one could consider mastery of oneself as the smallest mastery there can be; if one cannot master onself, one cannot begin to master anything beyond oneself. On the other hand, complete mastery of oneself is such an enormously difficult task that one could consider it to be greater than all others.
It's a big help.