Explain why your PE and KE are usually not both high at the same time (If PE is high then usually KE is low)

Might help:

an object can have both kinetic and potential energy at the same time. for example, an object which is falling, but has not reached the ground has kinetic energy because it is moving downwards, and potential energy because it is able to move downwards even further than it already has. as an object falls its potential energy decreases, while its kinetic energy increases. the decrease in potential energy is exactly equal to the increase in kinetic energy.

Does this your question?