Autobiographies are a special case where the end poses a seemingly insurmountable problem, unless a ghost-writer steps into the breach and writes it.
However, you can do it yourself. If you want to complete your autobiography, the first thing you must do is write the end.
The second thing you must write is the beginning.
The beginning and the end can be completed quite quickly as they contain the only indisputable facts in the story. The middle section will contain the most text, being a mixture of fact and fiction, and of indeterminate proportions of each.
Occasional random recollections and idle thoughts can be interspersed to update the text, and so the middle part is really a work in progress. This point, though, is unlikely to be evident to the eventual readers of your autobiography, to whom the text, as written, will seem to be complete.
As an example, here is my autobiography:
I was born at a very early age on Wednesday 10th January 1934.
At The Writers workshop of U3A Clarence, I once made some points about writing one's autobiography to a bright and intelligent group of oldies. Despite their advanced years, they quickly grasped the points of my argument and were 100% in agreement.
I died at a ripe old age on Saturday 27th October 2018.