“念念不忘”常见的英文表达有 “always on one's mind”、“never forget” 或 “have sth. constantly in mind”，具体使用可根据语境选择：
1、 always on one's mind
强调“持续惦记、难以释怀”，适用于情感或回忆场景。
例句：The memory of that day has been always on my mind.（那天的记忆一直萦绕在我心头。）
2、 never forget
直译“永不忘记”，简洁有力，常用于表达深刻记忆。
例句：I'll never forget the kindness you showed me.（我永远不会忘记你对我的好。）
3、 have sth. constantly in mind
突出“反复想起”，适用于持续思考或关注的场景。
例句：She had her goal constantly in mind and worked tirelessly towards it.（她始终牢记目标，并为之不懈努力。）
总结：若需强调“持续性”或“情感深度”，可用 always on one's mind；若侧重“记忆深刻”，可用 never forget；若描述“反复思考”，则用 have sth. constantly in mind。根据语境灵活选择即可。