ついついunintentionally, unconsciously, by mistake, against one's better judgement, against one's better judgment

お腹(なか)が空(あ)いてついついお菓子(かし)を食(た)べてしまった。

I was hungry and against my better judgment, I ended up eating snacks. {unintentionally, unconsciously, by mistake, against one's better judgement, against one's better judgment}

タバコを辞(や)めようと思(おも)いながらついつい吸(す)ってしまう。

Even though I'm thinking of quitting smoking, I end up smoking unintentionally. {unintentionally, unconsciously, by mistake, against one's better judgement, against one's better judgment}

美味(おい)しそうなケーキを見(み)るとついつい買(か)ってしまうのです。

Whenever I see a delicious-looking cake, I end up buying it unintentionally. {unintentionally, unconsciously, by mistake, against one's better judgement, against one's better judgment}

急(いそ)いで帰(かえ)らなければならないのについつい友達(ともだち)と話(はな)し込(こ)んでしまった。

Even though I had to hurry home, I unintentionally ended up having a deep conversation with my friend. {unintentionally, unconsciously, by mistake, against one's better judgement, against one's better judgment}

このカフェの居心地(いごこち)が良(よ)すぎるせいで、ついつい長居(ながい)をしてしまいました。

Due to the comfortable ambiance of this cafe, I unintentionally ended up staying longer than I had planned. {unintentionally, unconsciously, by mistake, against one's better judgement, against one's better judgment}