The most important virtue to uphold and trait to acquire in Ramadan is Sabr, steadfastness/perseverance/self restraint/patience.
In ramadan, its somewhat easy for a lot of us to engage in as much worship as possible with soo much zeal and humility. Post ramadan, it becomes a task. Over burdening sometimes. Now, it may be due to the absence of shaytan in ramadan or the fadl in the month, Allah knows best.
Sabr then is a trait we should aim to leave ramadan with as it will help us when the struggle returns after ramadan to keep up good deeds.