"a smooth sea never made a skilled sailor" meaning in English

{
  "etymology_text": "Attributed to Franklin D. Roosevelt.",
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      "expansion": "a smooth sea never made a skilled sailor",
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  "lang": "English",
  "lang_code": "en",
  "pos": "proverb",
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          "name": "English entries with incorrect language header",
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      "examples": [
        {
          "ref": "L.K. Elliott (2015 March 23) Confessions of an Ex Hot Mess: 10 Steps to Beat Stress and Feel Your Best, FriesenPress, page 53",
          "text": "A smooth sea never made a skilled sailor and the same concept applies to a relationship. If you have a relationship where there is never tough times to work through together, there will never be an opportunity to gain strength within the relationship. Accept the good with the bad because it all happens for a reason, and will teach you something."
        }
      ],
      "glosses": [
        "Challenging experiences are the most educational and thus, ultimately, the most beneficial."
      ],
      "id": "en-a_smooth_sea_never_made_a_skilled_sailor-en-proverb-EqWKp20G",
      "links": [
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          "Challenging",
          "challenging"
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        [
          "experience",
          "experience"
        ],
        [
          "educational",
          "educational"
        ],
        [
          "ultimately",
          "ultimately"
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        [
          "beneficial",
          "beneficial"
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      ]
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  ],
  "word": "a smooth sea never made a skilled sailor"
}

{
  "etymology_text": "Attributed to Franklin D. Roosevelt.",
  "head_templates": [
    {
      "args": {
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      },
      "expansion": "a smooth sea never made a skilled sailor",
      "name": "head"
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  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "proverb",
  "senses": [
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      ],
      "examples": [
        {
          "ref": "L.K. Elliott (2015 March 23) Confessions of an Ex Hot Mess: 10 Steps to Beat Stress and Feel Your Best, FriesenPress, page 53",
          "text": "A smooth sea never made a skilled sailor and the same concept applies to a relationship. If you have a relationship where there is never tough times to work through together, there will never be an opportunity to gain strength within the relationship. Accept the good with the bad because it all happens for a reason, and will teach you something."
        }
      ],
      "glosses": [
        "Challenging experiences are the most educational and thus, ultimately, the most beneficial."
      ],
      "links": [
        [
          "Challenging",
          "challenging"
        ],
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          "experience",
          "experience"
        ],
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          "educational"
        ],
        [
          "ultimately",
          "ultimately"
        ],
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  "word": "a smooth sea never made a skilled sailor"
}