You can use sick leave for mental health.
Article 12.2(a) (https://www.wpea.org/uploads/7/0/4/9/70496281/wpea_gg_contract_2023-2025.pdf) allows sick leave for personal illness—which includes stress, anxiety, and other mental health needs. If you need a day for your well-being, you are entitled to take it.
No one can tell you your mental health “doesn’t count.”