In English, we usually rely on the verb "to become" to express a transformation. Spanish, however, uses different verbs depending on whether the change was intentional or out of a person's control.
"Volverse": Involuntary changes
When a change is involuntary, sudden, or deeply affects someone's personality or mental state, use volverse. You will often see it used with adjectives to describe someone becoming eccentric, distrustful, or paranoid.
| In the forest, the hermit used to talk to himself and became eccentric. | En el bosque, el ermitaño solía hablar solo y se volvió excéntrico. |
| The owner of the cabin became paranoid for no reason. | El dueño de la cabaña se volvió paranoico sin razón. |
| A lot of people believe that he became crazy and paranoid. | Mucha gente cree que se volvió loco y paranoico. |
"Hacerse": Voluntary changes
When a transformation is the result of a conscious decision or effort, use hacerse. It is most commonly used for changes in profession, religion, or adopting a specific lifestyle.
| He was going to work in the city, but he decided to become a hermit. | Él iba a trabajar en la ciudad, pero decidió hacerse ermitaño. |
| He wanted to take care of nature, so he became a vegetarian. | Él quería cuidar la naturaleza, así que se hizo vegetariano. |
Notice how hacerse shows an active choice (deciding to abandon the city or change a diet), while volverse describes a psychological change that simply happens to a person over time.