As I do synastry (comparison of two natal charts for a relationship) readings for different clients I make note of certain aspects that keep popping up. One aspect I see a lot of is person A's Sun being squared by person B's Neptune. The textbook definition of this connection is that Neptune is going to betray or mislead the Sun. But in the charts I've looked at (these have all been romantic relationships) it's really just the Sun person's trust issues that are being activated.
The Neptune partner is minding their own business, doing their own thing, but the Sun person has that constant thread of suspicion. This is a tough one to get around because it's subtle but we all know how incipient mistrust can slowly poison a relationship.
Even if the Neptune person is doing something fishy (not being clear on their intentions, hiding things about their past), it's up to Sun person to deal with it. The Sun provides the illumination and clarity. The Sun is the engine and has the final say on whether they work through their own suspicions, confront their partner, or walk away. It is usually the Sun person that requests a consultation with me. This is crucial because they usually end up feeling so undermined that they give away their power to their partner (who hasn't even asked for it).
Is this you? Are you feeling (or have you felt) trapped/hamstrung by your suspicions?