Podria o podia?

Podria o podia?
 

¿Me podéis ayudar entender unas cosas?


He aprendido que se dice "Podría haberlo cogido" to mean "I could have picked it up" with "podría haber..." each time but I've just read in a Grammar book that this means the possiblity seems remote.
Is it better to say "Podía haberlo cogido"? "Podía haber venido, si hubiera sabido" "I could have come, if I had known"
Which is better to use? "podría o Podía



"It's no wonder you're tired today, after doing so much exercise yesterday"

"No es de extrañarse que estes cansada hoy despues de haber hecho tantos ejercicios ayer."

Podría = conditional

Podía = past