とは限らない

A sentence or phrase + とは限らない can be used to express that something isn't necessarily the case, or isn't always true. It helps to remember that the verb 限る means "to limit" and think of it as "this situation isn't limited to..."

お金がたくさんあっても幸せとは限らない。貧しくても幸せな人もたくさんいる。
Having a lot of money doesn't necessarily mean you're happy. There are plenty of people who are happy even though they're poor.

両親や先生がいつも正しいとは限らないが、一応、アドバイスはもらっておいた方がいい。
Parents and teachers aren't necessarily always right, but for now, it's best to get their advice.

上手な選手がいなくても、負けるとは限らない。チームワークで勝てることもある。
Just because there aren't any skilled players doesn't mean they'll lose. Being able to win takes teamwork too.

日本語の先生がいつも日本人だとは限らない。とてもいい外国人の先生もたくさんいる。
Japanese teachers aren't always Japanese people. There are lots of very good foreign teachers too.