Everything happens for a reason?

On an everyday level everything happens as a result of cause and effect. Physical causes have physical effects, mental causes have mental effects.

We can observe physical and mental processes to see how states of mind and physical states flow over time. 

On a mundane level at least the processes are continuous, not discrete.

We do not observe things coming from nowhere, or jumping from one position to another without going through the intervening space.

But I digress.

The point is: everything happens for the reason that all things are linked, throughout time. Each event connected to each other, an endless mosaic, stretching out endlessly​, through space and time.

So that's pretty cosmic, but the "reasons" we have talked about so far are directly observable ones, not metaphysical or philosophical ones.

Such metaphysical purposes, I believe, are beyond the ability of science and direct observation to know. Instead, these are philosophical stances we can only determine individually.

That is, there is no universal rule WE CAN A PRIORI BELIEVE that involves metaphysics. Only a lifetime of experience can be used for that!