Am I understanding this correctly? しないと


There is a character, an older male, in this manga that I'm reading who uses
this phrase twice  
しないとな and the two lines are like this：  

>   1. お礼をしないとな  
>
>   2. お別れをしないとな  
>
>

The first line, he is referring to himself ( **I** should show my
gratitude)-->I understood it more like "It wouldn't do if I don't show my
gratitude" "I have/must...(among these ideas). It was more clear when the
character said his 2nd line which I interpreted as: Say your goodbyes/Say
farewell (note, he was directing this to another character that was with him).  
I hope I made sense...What exactly is the usage of と here? What does it
express? And does the 1st line sound okay with the interpretations I gave?  
Thank you!




This しないと is a omission of しないといけない. It means "must", "have to".

I think you understand it correctly.




This しないと is a omission of しないといけない. It means "must", "have to".

I think you understand it correctly.

