Don’t count your chickens before they hatch.

1. 解释

成语“count one’s chickens before they hatch”通常用于用于否定句中。上文中的“Don’t count your chickens before they hatch.”的字面上翻译是“鸡蛋还未孵，先别数鸡雏。”比喻为“对事情不要太早下结论”或者是“对某事不要高兴太早” 或“事情未成功之前，不要擅自打如意算盘。”此语也可以用作Don't count your chickens until they are hatched.

2. 例句

e.g. Don't count your chickens before they hatch. How many lottery tickets did you buy?

别太早下定论，你买了多少张彩券？

Ps ：Don’t forget it’s just your first day working here.中的working here是现在分词做后置定语。I feel better working in this company than the previous one.中的working in this company than the previous one也是现在分词短语，在这里做时间状语。