I liked the one before. There are many versions of this.

@@ -16,2 +16,2 @@
-<gloss>seeds you don't plant will never grow</gloss>
-<gloss>if you're not willing to put in the effort, don't expect anything in return</gloss>
+<gloss>if you don't put in the effort, don't expect results</gloss>
+<gloss g_type="lit">seeds you don't plant will never grow</gloss>

Or, subtle but closer:
> If you don't put in effort, you can't expect results.

I put in the long-form of the explanatory gloss under the theory that it's a marginally popular saying as-is.

But a shorter version would be:
> If you don't put in the effort, don't expect results.

n-grams (pretty well-known phrase, I think)
蒔かぬ種は生えぬ	1556

蒔かぬ種は生えぬ
https://dictionary.goo.ne.jp/word/蒔かぬ種は生えぬ/
何もしないではよい結果は得られないことのたとえ。

==============
100% of the Seeds You Never Plant Will Never Sprout
https://www.thehomesteadjourney.net/post/100-of-the-seeds-you-never-plant-will-never-sprout

Whether we’re talking life in general or we’re talking homesteading it rings true. 100% of the seeds you never plant will never sprout.  Many times we have these great ideas in our head, these visions of what we want to accomplish on our homesteads, but we never take that initial step. We never plant that seed to even give it a chance to grow and bring forth fruit. 

========
Lesson three: Seeds that you don’t plant don’t grow.
The same is true for everything else in life!
https://www.thebigwhisper.com/blog/2020/5/25/three-lessons-this-founder-learned-from-gardening-that-apply-to-life-and-business

========
It has been famously said that you miss 100% of the shots you don’t take; you miss the success of all the seeds that you don’t plant.
https://medium.com/wonderbite/atomic-habits-newsletter-18-8f155b7c8c45

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You can't be mad about not harvesting the seeds you DON’T plant.
https://andyfrisella.com/blogs/andygram/fill-your-mind-with-the-right-things

=====================
https://www.askmen.com/answers/dating/1632382-is-she-asking-to-hangout-tonight.html
She could just be asking to see if you are seeing anyone else, but you should go ahead and ask her. 100 percent of the seeds you don't plant don't ever flower.

======================
You Can’t Expect To Bear Fruit If You Don’t Plant Seeds
https://www.tblfaithnews.com/faith-religion/you-cant-expect-to-bear-fruit-if-you-dont-plant-seeds

=======================
If no one plants seeds there can be no fruit for the harvest!

=================== This one is cute =================
The seeds you don't sow won't grow! 
(link dead)
https://www.wedrinkandwefarmthings.com/shop/the-seeds-you-dont-sow-garden-notebook

I've just proposed an entry for "nothing comes from nothing", which has a standard translation into Japanese:
無からは何も生じない

"Nothing comes from nothing" seems to be primarily a philosophical argument about the nature of creation, and much less a parable about the importance of effort and/or hard work.  See my comments on the 無からは何も生じない entry for more details, I do not think these entries should be linked.

By prettying-up the "literal" gloss ever so slightly, I don't think any further glosses are necessarily needed.  I think the meaning is self-evident, all of my English-language references are just examples of this idea.  I don't think there is a "fixed" English equivalent, though.

Googling around, I found a somewhat catchy English-language gloss that is floating around the internet.  The source is unknown(anonymous). I think the literal gloss stands well enough on its own, so I wouldn't mind if the explanatory gloss is dropped, but maybe it's helpful to include anyway.

If the old gloss goes back, I think the word "good" should be inserted (よい結果は得られない)
> don't expect [good] things to happen on their own

====

Small note on Rene's comment(2017) - I would avoid any expression based on "reap what you sow" here.  This pair is almost always used with a negative connotation.
Google...
idiom. : to experience the same kind of things that one has caused other people to experience. If you're rude to everyone, you'll reap what you sow.

@@ -16,3 +16,2 @@
-<gloss>nothing comes of nothing</gloss>
-<gloss>don't expect things to happen on their own</gloss>
-<gloss g_type="lit">the seed you don't plant doesn't grow</gloss>
+<gloss>seeds you don't plant will never grow</gloss>
+<gloss>if you're not willing to put in the effort, don't expect anything in return</gloss>