Possess a perpetual fountain and not a mere well

The George Long translation of 1862: 

If a man should stand by a limpid pure spring, and curse it, the spring never ceases sending up potable water, and if he should cast clay into it or filth, it will speedily disperse them and wash them out, and will not be at all polluted. How then shalt thou possess a perpetual fountain and not a mere well? By forming thyself hourly to freedom conjoined with contentment, simplicity and modesty.  Marcus Aurelius.  Meditations.  Book 8.

Chrystal's 2017 rendering based on the Foulis translation of 1742:

What if some one, standing by a clear sweet fountain, should reproach it? It would not cease to send forth its refreshing waters. Should he throw into it mud or dung, it will speedily scatter them and wash them away, and be in nowise stained thereby. How then shall you get this perpetual living fount within you? If you reserve yourself unto liberty every hour you live, in a spirit of calmness, simplicity, and modesty.  Marcus Aurelius.  Meditations. Book 8.

Image: Hylas and the Nymphs, a Gallo-Roman mosaic, 3rd century CE, in the Musée of Saint-Romain-en-Gal (France) courtesy of Wikimedia Commons contributor Vassil.