What is stopping me from putting away in a saving account (or any separate account) some 20-30 bucks every month/year so I can retrieve them later in case I nee

What is stopping me from putting away in a saving account (or any separate account) some 20-30 bucks every month/year so I can retrieve them later in case I need them to replace my laptop/phone/tablet/whatever, instead of giving more than what I'd need to somebody else and effectively lose that money?