Aw don't be too hard on yourself! You're doing great so far, so don't let that get you down! Yes, it does take time and feel, but don't let something small like that bug you, I do it all the time.
What I try to work on, is do sitting trot, then start posting, but as I go up, I look at the corner of my eye to make sure I'm going up with his outside leg. Try doing that, and focusing on the "feel" of rising at the quick moment his leg does.
Something else you could work on, is getting him into a nice stretchy trot, and posting on the wrong diagonal, then switch, and focus on the feel. Usually on the wrong diagonal you don't feel the "bounce" that pushes you up when you rise.
"In the end, they're only going to remember you for the times you smiled when you had every reason to cry."