The Maine is an American Rock Band formed in 2007. "Some Days" is a song where the words which are undeniably poetic, if corny, have perhaps been used , more for their ability to fit with the tune and the rhythm than for their deep meaning.
The use of simile (comparing two things with "like" ) allows the words to create a visual picture. Lemonade is associated with families picnicking by the lake in the Summer; possibly even homemade lemonade. In sharp (no pun intended!) contrast to this, razorblades can harm you and the fact that it follows on immediately from this family- inspired vision makes it even more poignant. Razorblades are sharp and unforgiving. One small mistake and there's likely to be blood everywhere. The writer of these lyrics wants the listener to understand the pain that can creep up on you from nowhere and really hurts.
These words form the chorus so are repeated to add emphasis to their intensity. The writer sometimes wants to escape his life; whether it be "lemonade" days or "razorblade" days - if he could just "float away." Note that it is only "some days" though!