I don't mean missing Fajr prayer, or back-biting. These are clearly bad.
No, I mean the things that you habitually do, that you maybe know might, perhaps, just maaaaybe wrong. but your mind somehow makes okay.
The litmus test: the month of Ramadan.
If you feel truly uneasy doing this deed in Ramadan, it's most likely a sin.
If you have the self-control to give it up completely, Masha'Allah, it's 99.9999% likely a sin, or at the very least, a waste of your precious time.
So, really, let's reflect on that for a moment. If the above is true, then we should ideally never resume committing those doubtful acts after Ramadan, right? I mean, what's a sin in Ramadan, is still a sin on Eid day, and onwards still.
If gold, and diamonds, and oyster pearls are precious by their rarity alone, then it is clear that every moment we exist, every breath we inhale, then exhale after that, is pure gold dust, if only because they are all rarer than the rarest gemstones; never to be seen again, until the day that our deeds are played back to us on the ultimate cinematic, widescreen, surround sound, ultra high def experience of Yaum al-Qiyamah(The Day of Judgement).
So what makes those acts that seem wasteful in Ramadan, suddenly become a good use of our time after the month has swiftly past through our fingers?
What validation do we put forth for our thinly veiled hypocrisy?
Weakness? Perhaps. We are made weak. But still. We have a month to train hard. To build up our spiritual muscles. Yes, you can get that emaan six-pack you always wanted - and in just THIRTY DAYS, insha'Allah!
So, take another look at that mental list you wrote; the one titled, "What I plan to give up during Ramadan", and ask yourself: "If I can last 30 days without it. and with it, my Ramadan is tainted then is it really that important to me? And do I really want it back in my life ever again?".
The Messenger of Allah Muhammad(peace be upon him)said: "Righteousness is good character, and sin is that which wavers in your heart and which you do not want people to know about." [Muslim]
The Messenger of Allah, sallallahu 'alayhi wasallam, said to his Companion: "You have come to ask about righteousness ?" "Yes," I answered. He said: "Consult your heart. Righteousness is that about which the soul feels tranquil and the heart feels tranquil, and sin is what creates restlessness in the soul and moves to and fro in the breast, even though people give you their opinion (in your favour) and continue to do so." [A good hadith transmitted from the Musnads of the two Imams, Ahmad bin Hanbal and Al-Darimi]
May Allah guide us to the true answer to those questions, and make it easy for us all to do the right thing.! Ameen