Well, what is pleasing/acceptable to oneself is also one of the means of Dharma just like the scriptures (or the scriptural injunctions) are.
Because, Manu Smriti 2.12 says:
वेदः स्मृतिः सदाचारः स्वस्य च प्रियमात्मनः ।
प्राहुः साक्षाद् धर्मस्य लक्षणम् ॥ १२ ॥
vedaḥ smṛtiḥ sadācāraḥ svasya ca priyamātmanaḥ |
etaccaturvidhaṃ prāhuḥ sākṣād dharmasya lakṣaṇam || 12 ||
The Veda, the Smṛti, the Practice of cultured Men, and what is
agreeable to oneself—these directly constitute the fourfold means of
which should be our preference? Can I take a decision which is
agreeable to me which is not sanctioned in the scripture. There is an
example I gave you in the question.
The example given in the question is this:
For example : After returning from my work, I feel my body is smelly
due to sweat and I should take a bath. But the time prescribed has
already past. And many more situations like this.
What we need to understand here is that when scriptures say bathing in night is forbidden then that injunction refers to a "ritual bathing" which is aimed at attaining ritual purity.
A ritualistic bath is preceded by a Sankalpa. It is done while holding the Kusha grass in hand. It is done while submerging the head in a water body. Therefore, the bath that we take in a shower cabin in today's time is not really a ritual.
One has to see the following Parashara Smriti verses:
Bathing in the daytime, while being purified by the rays of the sun, is the approved form of bathing. Bathing at night is not approved
unless when the Rahu is visible in the heavens.
Bathing, making of gifts, austerities, and burnt-offerings, may be made at night when an eclipse is seen. Night otherwise is impure ;
therefore night is to be shunned in performing rites.
So, when bathing is ritual it is forbidden to be done at night.
Now, what is the reason that a ritualistic bath is forbidden in the night?
- The Maruts, the Vasus, the Rudras, the Aditya, and other deities, all disappear with the moon. Therefore, gifts are not proper at night.
The Vedic deities are said to disappear at night and that is why rituals, whether it is making gifts (charity) or even bathing, are disapproved during that time.
Now, does that mean if a hungry man comes to you during night giving him food is an act of sin? No way.. Because it is not a formal and ritual charity that you are making here.
The same logic applies when it comes to a bath that is a necessity of the body and mind and not a ritualistic formality.
If the body is sweaty and dirty after a soccer session (say) at night then there is nothing wrong in having a bath. Because, one should aim at remaining pure all the time and sweat is one the impurities of the body.
Manu Smriti 5.135. Oily exudations, semen, blood, (the fatty substance
of the) brain, urine, faeces, the mucus of the nose, ear-wax, phlegm,
tears, the rheum of the eyes, and sweat are the twelve impurities of
He should not do so while he or the person greeted is seated, lying
down, or impure. If he is able, he should not remain impure even for
a moment (A 1.11.32 n.) - Baudhayana Dharmasutras 1.3.13