In the following situation, which fits best (should or must or have to):
I think that it is very important to look after the environment. This means that we should/must/have to cut down the amount of waste that we create.
I was taught that we use have to to express strong obligation, when the obligation comes from someone else.
And that we use must to express strong obligation, when the obligation comes from you.
And to use should to express mild obligation.
Accordingly, it is (MUST) that fits best, but I am still not sure about that.