It means " I can't be more happier" in this sentence.
Sometimes it means "I don't have enough time to do something"
There is a romance novel call "
来不及说我爱你“ means " I don't have enough time to say I love you"
Sometimes it means too late to chatch up/ do something like "你再不快一点,上班就来不及了” means If you don't hurry up, you can't go to work on time."