I had another question as well . If someone makes a promise to Allah (swt) and this promise is not a nazr (eg- I will do so and so , if so and so work of mine is done) ; just a general promise , eg- of reciting a particular day every day – ie, the person promised Allah (swt) that they will recite a particular dua everyday , but he doesn’t end up keeping the promise – he does not recite the dua- then is there any sort of Kaffara to be paid for this , and is the person liable for any punishment because he has not kept the promise ? If he continues not to keep the promise , is this a sin?

They should seek istighfar and make sure they don’t repeat it again