I am looking at a story written in the past tense which I think needs to use some present tense statements.
Consider these example sentences:
Everyone has choices.
She grieves for his memory.
She must do this.
I think the first two are needed to convey that those things are not changeable, almost everlasting truths.
The third is tricky because the modal verb 'must' has no past tense. The closest you can get is 'She had to do this.' I think the 'must' version is technically ungrammatical but works better to convey a sense that no other option exists.