I am writing a fiction story in first person with the narrative in past tense but I find I want to use many words that indicate present time such as now, this, tonight, tomorrow, etc. I've seen this in some fiction novels, but I've heard from some people that this is mixing tenses. Here are some examples:
"Now, I didn't know what to think."
"I knew this time, once school resumed..."
"He was supposed to start school today."
"They were now happy to remain on the easy runs."
"She was now practically running."
"This would give me a full day... "
I would like the novel to have a present feel rather than feel it is being told about a distant past... but I want to be grammatically correct.