Sometimes they can see things you can not. The key is a trusted friends whose opinion you value. If you are stressed out all the time with the person you are with then you may be with the wrong person. That is not what relationship is about. You are supposed to enjoy being with them most of the time.
Relationships are up and downs.
You may go thought some difficult spells. But overall, the relationship should be pretty good. If things are not going good with someone and relationship has been declining over a period of time. Then do something to fix it. You can waste years of your life, coasting in a relationship.