Basically, since all thoughts are not within our control, there is no point ruminating over negative thoughts about past/future/etc since there is no "subjective" reason why these negative thoughts show up, they show up simply because of hormone levels/neural firing/genetics/external stimuli/etc, and ruminating over them will simply reinforce them with no any benefits. There is no need to blame why you have those thoughts, since they are just there due to physical laws which have nothing to do with you as a person.
On the other hand, when a positive thought emerge, although we know it has nothing to do with ourselves, it does not harm to enjoy it at the moment.
by Illustrious-Pay-7516