I’ve been learning English for years but still am confused about when to use plural... I found this sentence in an article: “Force yourself to make hard decisions and delete any task that does not lead you toward your mission, your values, and your goals.” Why this sentence doesn’t say “missions” but “mission” while plurals are used for “values” and “goals”. Also, will it be weird if I said “Force yourself to make a hard decisions”
In your example it is assumed you have one singular mission or end goal, but you may have to make many different decisions and actions to reach it. So, 'mission' is singular, but the decisions and tasks are spoken of in plural
Literally, a 'mission' is a job that you are sent on, and so it is not common to be engaged in more than one mission at a time because you cannot be 'sent' to multiple locations at the same time. In the original military context, if a person was to be tasked with multiple mission, they would still likely have a 'primary mission', and other secondary, or 'side' missions. This may be why it is more common to see 'mission' in singular form.