actually starting stuff. like when you're initially progressing from flirting to the actual realised concept of love, and you want to back out desperately but you stay. from there it's all fine because you really begin to love them, but that shit is TERRIFYING.
also the lack of communication/mutual trust. like when people refuse to vocalise what they have on their mind - and it leads to built up resentment that seeps out in interesting ways. it breaks down the relationship slowly. if you cannot communicate, that is a problem with you and should therefore be resolved by you. lack of communication correlates with lack of trust, and will cause nothing but a host of problems