Is it permissible to supplicate for marriage to a specific girl, and does a lack of psychological comfort regarding this indicate a lack of acceptance of good deeds or the commission of sins?

There is no harm in a man loving a woman, provided he keeps himself chaste from the unlawful, and he will be rewarded for that. It is permissible to supplicate for a wife, while being cautious not to be drawn into the forbidden by excessive thinking about her. Psychological discomfort is not necessarily an indication that deeds are not accepted, and striving to cease thinking about her will bring comfort. It is recommended to frequently remember Allah, seek forgiveness, fill one's time with what pleases Allah, and keep company with righteous people.