Memories can make you smile, but it can very well make you cry hard. Memories can make you smile, but ... there is a good chance/high probability/likely/possible ... that the memories will make you cry hard. The term "very well" is usually used in formal speech. It's usually used with verbs that say that something is true or possible... verbs such as: may, might, could, would, should, can. "may (very) well/ may (very) easily" - is used for saying that something is likely to be true (possibly true) or is likely (might or may) happen... For example: What you say may very well be true. [There is a good possibility that what you say is true] A small technical error may very well (easily) result in a serious accident. It might very well be true that the information is not available. I could very well improve my Chinese language skills if I studied 24 hours per day :) Good question Tingting... I hope my answer helps

Here, very well means 'equally' or 'just as easily'. Say a replacement football player is put in the game because the main player gets injured. An announcer may say to the fans, "well, here it comes ___. This could turn out badly for us, but it could very well turn things around to have some fresh energy on the field."