Gemara:Before you get hungry, eat. Before you become thirsty, drink. When you first need to urinate, do so promptly.

Ein Ayah:It is appropriate for all people to "listen to the voice" of his internal feelings, as the Creator gave us these feelings to protect us from bad things and to lead us on the path of life. The idea of listening to internal signals applies to matters of the body and to matters of the spirit in a manner that there is overlap between the two of them.
Sometimes a person’s mind will be tuned in to matters that are of direct practical import, such as matters of practical halacha. This is hinted at in the Rabbis’ statement about eating when hungry, as bread can be a reference to halachic rulings (see Chagiga 14a). Other times a person will find himself drawn to matters of song and aggadic discussion, which bring a person to cling to Hashem and feel holy and pure feelings of love and fear of Hashem. That phenomenon is hinted at in the idea of thirst for water (ibid.). A person should leave time for each of these spiritual desires according to his internal feelings. The desire for a specific matter is a sign that the person is missing something in that area of spiritual involvement. This is included in what the Rabbis instructed to eat and drink when those feelings presented themselves.
Sometimes a person will feel a need to concentrate on an area in which he sinned, and he will have an urge to remove the element of sin that may have attached itself to him. He may then turn to prayer, supplication, and admittance of his wrongdoing. He should not delay such a feeling, to remove the bad and the spiritual waste from within him, to purify his spirit before his Maker with a feeling of spiritual strength. This is included in the instruction to remove the waste when one has an urge to do so.