When you share a good secret with someone, it engenders trust and even love. The longer the secret stays between you two, the greater the chances of these feelings arising and flourishing. This is part of the reason the love between husband and wife increases over time. Over the years, you share experiences and moments that no one else is privy to. And you know things about each other that no one else knows. This sharing becomes its own source of love and affection.
We should also make a concerted effort to develop this relationship with our Lord. To do this, entrust Allah with an important secret: Do a special good deed with the intention of keeping it hidden from all others. This is one of the many virtues of qiyamul layl, i.e., the night prayer (may Allah give us all the tawfiq to pray in the dark of night). But even if we don’t do qiyam, any other good deed will suffice (consider the hadith of the three men trapped in a cave). The bigger the deed, the bigger the secret, the bigger the potential that Allah will accept. Same thing for small but consistent good deeds.
In the end, we already share secrets with Allah in the sense of Allah, out of His mercy, shielding our sins from view. But we need to do our part to counterbalance that with good secrets.