A fountain gets muddy with but little stirring up, and does not get clear by our meddling with it but by our leaving it alone. The best remedy for disturbances is to let them run their course, for so they quiet down.

[Una fuente con poca inquietud se enturbia, ni se volverá a serenar procurándolo, sino dejándola. No hay mejor remedio de los desconciertos que dejarlos correr, que así caen de sí propios.]

Baltasar Gracián y Morales (1601-1658) Spanish Jesuit priest, writer, philosopher
The Art of Worldly Wisdom [Oráculo Manual y Arte de Prudencia], § 138 (1647) [tr. Jacobs (1892)]
    (Source)

(Source (Spanish)). Alternate translations:

A Well will be troubled if it be in the least stirred, and its water becomes clear again, by ceasing to dabble in it. There is no better remedy for some disorders, than to let them alone. For at long run they stop of themselves.
[Flesher ed. (1685)]

A fountain gets turbid by a little movement, and does not become clear by our trying to make it so, but by our leaving it to itself. The best remedy against discord and confusion is to let them run their course, for so they quiet down.
[tr. Duff (1877)]

It takes little to muddy a spring, nor does it clear by being stirred, but by being left alone: there is no better remedy for turmoil, than to let it takes its course, for so it comes to rest of itself.
[tr. Fischer (1937)]

It takes little to muddy a stream. you can't make it grow clear by trying to, only by leaving it alone. There is no better remedy for disorder than to leave it alone to correct itself.
[tr. Maurer (1992)]