〜ばよかったです

ばようかったです means I wish I had done or I should have done something. You can use it to describe an alternative course of action you, to your regret, did not take.

あのとき、あいしているといえばとっかたです。

I wish I had told her that I loved her.

All verbs can regularly be turned into a ばよかったです sentence with no exception or irregularity. YOu form the ば-form on the basis of the present tense short forms.

Verbs in the affermative:

Drop the う and add: えば:　　たべる -> たべれば

Verbs in the negative:

Drop the final い and add ければ:　　 たべる -> たべなければ