It has its benefits:
Since the bilingual brain is adept at suppressing the language that isn’t being used in a given moment, it has experience inhibiting unhelpful information and promoting important stuff. There are lots of benefits to this — one study found that bilinguals were more able to filter out ambient noise. Speaking two languages means you feel less overwhelmed when trying to order in a busy restaurant, and makes you more capable of talking to someone on a crowded subway.
Bilingualism can also help delay the effects of Alzheimer’s:
[L]anguage multiplicity appears to hold off the effects of dementia. In one examination of 211 probable Alzheimer’s patients, the effect was so great, she found that the bilingual patients had reported the onset of symptoms 5.1 years later than the monolingual ones.