Can I turn off streaks?

Yes. Open Settings → Preferences → Streaks & Badges and turn off Show streak. Your streak no longer shows on Home or your profile, nothing celebrates it, Streak Reminders stop, and Home's greeting no longer counts days in a row. Your buddies' streaks are hidden too, and yours stops being shared with them. Nothing is lost: your streak comes from your plans and the time you log, so turning Show streak back on shows it again right away, unless it ended in the meantime. The setting follows you to your other devices when sync is on. To hide badges as well, turn off Show badges on the same screen.