A sword isn't forged in a day

Don't sabotage yourself by putting in too much effort

In Japan the phrase 頑張って (Ganbatte: Do your best) is used a lot. These words of encouragement that can be used for more or less anything from opening a particularly stubborn jar to running an ultramarathon.

One phrase you might not hear as often is the phrase 頑張り過ぎないで (Ganbarisuginai de: Don’t try too hard).