Anytime you give abundantly of your time, love, money or energy, you will activate resentment if you get nothing in return but unmet expectations. You may blame it on them, but underlying it all, you are basically upset with yourself for continuing to devalue your worth by not stopping whatever it is you are doing for them.
When we feel resentful, we erect walls that block gratitude. To prove yourself right, you then look for where they are failing you, and everything they do or don’t begins to irritate you. To break this, stop blaming them and take responsibility. You can either stop expecting them to be someone they are not, express yourself lovingly to them, or reset the rules of engagement. Easier said than done, I know, but do nothing and you are the only one that really suffers.