Let's break each other free from our past, So we can look forward instead of back. I'm not trying to steal your heart, So you don't have to stay on guard. If you let all your emotions un-bottle, I Promise there won't be any bad side effects. But if you happen to fall, Then I'll bring colors to your world. Then we can enjoy it like spring, We're mature so it won't be past tense. Just take a chance, Let's have this dance, Never know it may be the last....
The line "We're mature so it won't be past tense" is used as a pun as past tense of spring is sprung (To fall heads over heels), at the same time it is saying that it won't be like the past.