advice from a novice:

stop thinking that you're good enough for your significant other. why? because they already have a default notion of the perfect guy/girl. and this perfect person is you on a good day, everyday. so don't think it's your fault, but just know that these expectations are impossible to fulfill 24/7 7 days a week. so don't be so hard on yourself, but all the same, don't become complacent in your relationship.  Because you may think that you two are perfect for each other but if you stop putting in the extra effort, or any effort for that matter, things will go sour and the default person will come to mind and your significant other will convince themselves that they deserve better. [which is your fault because you were a better person when you didn't take them for granted].

p.s. 

happy month-a-versary to my lover. although we never spend the 5th of any month together.