Standing in Ramadan
مَنْ قَامَ رَمَضَانَ إِيمَانًا وَاحْتِسَابًا غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ
Man qama Ramadana imanan wa-htisaban ghufira lahu ma taqaddama min dhanbih.
"Whoever stands in prayer during Ramadan out of faith and seeking reward, his previous sins are forgiven."
Narrated by Abu Hurayrah. Sahih al-Bukhari 37, Sahih Muslim 759
A short reflection
Taraweeh has the same two conditions as fasting. Iman and ihtisab. Belief in the One you stand before, and a heart that is not counting reward in advance.