Have you thought about taking something along with you that you can hold to help comfort you? A stuffed animal, a photo of your family, or anything that makes you feel better.

The FAs have to sit in their jumpseats during takeoff, so they can't sit with you unless there is an empty seat.

The person sitting next you you might let you hold their hand/arm during takeoff. It may be embarrassing to ask, but it's an option.