What's "heavy lift" mean here?

Native speaker’s answer
Rebecca
Here "heavy lift" refers to a "burden" or "expectation." They're saying metaphorically, it's a lot to carry and handle by one's self. Ex: It's a heavy lift to look after my siblings for the whole weekend. = It's a big expectation to look after my siblings for the whole weekend. Ex: Moving by yourself is a heavy lift. Are you sure you don't need help? = Moving by yourself is quite a burden. Are you sure you don't need help?