Smart Saver is a solution that you might tap into on occasion due to regular fluctuations in spending. It’s designed to hold extra money you have lying around, which you’d like to have grow some, so you’re not leaving easy money on the table. This is the money you use when a small appliance randomly breaks or you take a weekend vacation. You should be okay dipping into Smart Saver from time to time.
A Betterment Safety Net goal is the money you save for big emergencies. There’s a set amount you want sitting in it (usually 3-6 months of expenses), that hopefully, you’ll never touch. It needs to grow to keep up with inflation and presumably your income growth. This is the money you use if there’s a big medical emergency, you lose your job, and/or if there’s a natural disaster. There should be a mental barrier that says, "I only touch this account for true emergencies."