Are the possibilities for self improvement endless?
The human personality is in a constant state of change. The only constant in the universe is change. Does this mean that technically one is able to drastically alter their personality and way of seeing and perceiving and responding to the world? Most people stay relatively the same over long periods of time, but is this because their environmental triggers usually stay relatively the same over long periods of time?
No. They are not endless. Some things do not need improvement. Some things are exceedingly difficult. And the human life-span is limited.
Possibilities are limited by available resources and opportunities.