Am I praying tahajjud correctly?

Am I doing something wrong that my tahajjud dua never comes true? am I praying tahajjud right? I start by praying 2 rakat then 1 witr then read the tahajjud dua and start with the normal way of making dua with praising Allah and prophet Muhammad SAW then ask for forgiveness then say my dua then ask for forgiveness again then end it with praising again and read the tahajjud dua again. is this correct? I dont ask for anything bad.