The particles 「と」「ば」「たら」「なら」are the almost same function and the core meaning is "if". 「人に合わせないと不安」 means "I am uneasy if I go a different way from people." This is the answer of you!! https://japanese.stackexchange.com/a/1784/38911
– Mitsutoshi WatanabeMay 28 '20 at 12:32