Cutting It Short: Pick a tense. Past. Present. Whatever, just stick with it. There are times it can be broken, but not by the narrator.
How sorry I felt for my proof-reader when I saw all the red marks of changing past tense, and present tense. I wove them together like a professional basket weaver, and it was a disaster.
Pick your tense. It can be past, it can be present. Sometimes, only sometimes, can you change those, but make it clear where you’re going before doing so.
Examples are going to be the best way to explain this. See below:
“She escaped from the clutches of death with the thought of him on her mind, and in the seconds it took for life to return to her lungs, she knew she would never be the same.”
— Past tense. The narrator is telling you something that has happened.
“She escapes the clutch of death with the thought of him on her mind. The seconds it took for life to return to her lungs, gave enough time for her to know she would never be the same.”
— Present tense. The narrator is telling you something happening at the very moment.
“She escaped the clutches of death with the thoughts of him in her head. The seconds it took for life to return to her lungs, gives enough time for her to know she would never be the same.”
— Mixed tenses. The narrator is not giving you a clear idea if this is happening now, or if this happened in the past.
“I remember how I escaped the clutches of death,” she says with a far off look in her eye, “it was you I was thinking of.”
Her eyes find his, and he can see the depth of her longing. He breaks the connection between them, and crosses his arms as he looks down, “I can’t hear this right now,” he shakes his head, the weight of where they are pulling him down. He looks up again, and pulls in a long breath as he turns, and walks away.
“I knew I’d never be the same after that,” she says under her breath, watching him leave.
— Mixed tenses. This works because the character is the one referencing the past tense, while they are in the present.
Hope this helps in your tense situation.
As always, I’m open to banter.