Mainting tenses continuity...

I'm working on a Fantasy story and I've been trying to keep the dialogue in the present and using the past tense for the narration, 3rd person limited.

I try to keep the narration a mix of simple past, past perfect and past continuous but I keep finding myself wanting to shifting to present especially while describing a series of events over a timeline. Am I overthinking this? Does it matter if theres some tense slip up ?

How do you makes sure you stay true to form while telling a story?