The purpose of a sitting meditation session is that one continues the practice for the rest of the day.
Following 4 factors, though used in a slightly different context in the quoted text, may help in trying to extend your practice to daily session:
- Concern (ābhoga): you pay initial attention to the breath, you apprehend the breath, you advert the mind towards the breath, to the effect: ‘I will try to make the breath tranquil.’
- Reaction (samannāhāra): you continue to do so, i.e. you pay sustained attention to the breath that way, do it again and again, keep the breath in the mind, to the effect: ‘I will try to make the breath tranquil.’
- Attention (manasikāra): literally ‘deciding to make the breath tranquil’. Attention is the mental factor that makes the mind advert towards the object. Attention makes the mind conscious of the breath and know the breath.
- Reviewing (paccavekkhaBa): you review (vīmamsa) the breath, make it clear to the mind, to the effect: ‘I will try to make the breath tranquil.’
p35/36 Knowing and Seeing by Pa-Auk Tawya Sayadaw
In the context of your question:
- Concern - one should be concerned to retain the object of mentationmeditation may it be breath or metta
- Reaction - one should see if one's mind is with the object and if not bring it back. Even if not periodically are apply your mind to the objects by trying to see the meditation object (in the case of breath / ) or be with the meditation object.
- Attention - one should pay attention to what the mind is doing, i.e., wandering off or staying in focus
- Reviewing - periodically are checking if you are at it
Also, you can try extending to other Brahmavihara meditation to remove impatient reaction and irritation as they can be not only due to ill will but due to other factors like cruelty, discontent and aversion. E.g. one sees someone with a better car which might be irritating. Something being better than mine give arise to discontent.
(1) Rāhula, practise the cultivation of lovingkindness. For when you cultivate lovingkindness, any ill will will be abandoned.
(2) Rāhula, practise cultivation of compassion. For, when you cultivate compassion, any cruelty will be abandoned.
(3) Rāhula, practise the cultivation of gladness. For, when you cultivate gladness, any discontent will be abandoned.
(4) Rāhula, practise the cultivation of equanimity. For, when you cultivate equanimity, any aversion will be abandoned.