can't win 'em all

(You) can't win 'em all. AND (You) can't win them all. — и на старуху бывает проруха; ~ не везет в картах, повезет в любви

Example 1: I'm a bit disappointed I didn't get the job. Oh well, you can't win 'em all.

Example 2: Mary: Gee, I came in last again! Jane: Oh, well. You can't win them all.

Example 3: "Can't win 'em all," muttered Alice as she left the boss's office with nothing accomplished. (McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.)

Also
[win some, lose some]
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The you is impersonal, meaning one, anyone. The apostrophe on 'em is not always used.)