Add profiles once:
aws configure --profile work
aws configure --profile personal
They land in ~/.aws/credentials and ~/.aws/config. Use one per command:
aws s3 ls --profile work
Or for the whole shell session:
export AWS_PROFILE=work
Check who you are before you do anything destructive:
aws sts get-caller-identity
For SSO accounts, aws configure sso sets up the profile and aws sso login --profile work refreshes the session.