“When life gives you lemons, make lemonade” is supposed to be about making the best of a bad situation.
But, having lemons is not, in fact, a bad situation. People willingly buy lemons all the time, in order to have them. Lemons are great.
Secondly, you need a *lot* of sugar to make lemonade. The best you can do otherwise is make lemon juice. So having lemons alone isn’t enough.
A more accurate phrase would be, when life hands you a crushing blow, expect dickheads telling you to perk up.