I'm sorry, but the song "Step Inside Love" is not written or performed by Elvis Costello. It was actually written by Paul McCartney and recorded by British singer Cilla Black in 1968. The song was written as the theme song for a British television show called "Cilla," which starred Cilla Black herself. The lyrics of "Step Inside Love" convey a message of love, comfort, and togetherness. The song invites someone to step inside love and find a place where all their daily worries can be taken away by the happiness reflected in their partner's smile. It suggests that love provides a sanctuary where one can find solace and warmth. The lyrics also emphasize the idea of being there for each other, whether it's in times of tiredness or when one needs someone to lean on. The singer expresses their enduring presence, assuring that they will always be there day and night if needed. Additionally, the lyrics touch on the bittersweet feeling of parting, expressing hope that they will be reunited again and reassuring that even when apart, they will miss each other until they can be together once more. Overall, "Step Inside Love" is a heartfelt love song that encourages taking refuge in love, ensuring unwavering support, and cherishing the moments shared with a loved one.