You may never become a “shower”. Remember the difference between a shower and a grower is the percentage difference from flaccid to erect, Not the absolute size of either.
I find that the terms grower and shower are often misused. For instance, a 4 inch flaccid that grew to 5 would probably be considered a shower while a 4 inch flaccid that grew to 8 would technically be a grower. If you are 6 erect and you increased your flaccid size from 3 to 5 but your erect length was unchanged, that would technically be a conversion from grower to shower, not usually a common goal.
When most people talk about becoming a shower they are just referring to the desired increase in flaccid size.
You may never change the personality of your penis but you will most likely increase both flaccid and erect measurements through PE.