Every once in a while I get these terrifying thoughts that despite all my good intentions and efforts to obtain paradise, I could still be sentenced to hell and that I am a terrible person no matter what. What should I do?
Terrifying thoughts are from Satan to disturb the believer and they do not lead to hell unless you believe in them. When you call such thoughts as terrifying, it means that you are terrified by them and never pleased or accepting them.
'Keep on repeating Estighfaar, Salawaat and LA HAWLA WALA QOWWATA ILLA BILLAH.
Wasalam.