A lot more relaxed in the two's and generally a better player. I have no doubt the standard has a lot to do with it but sometimes I do come up against first team bowlers in the two's and have a lot more success.
So try and play my natural game, don't pre-meditate a defensive stroke, relax and watch the ball...
Without seeing you and the bowler in action, it is hard to say what you are doing wrong and what would remedy your situation. Regarding playing quicks, here are a few tips that helped me:
1. Practice against a Bola. Set the machine on the highest speed you are comfortable with and play different shots. I leave the machine at one speed/swing setting and move around a bit in my crease to simulate different lines and lengths from the bowler. Once you are comfortable at a speed, try a higher speed. I use increments of 3 mph when drilling. Challenge yourself in your practice, push yourself outside your comfort zone. Your goal should be: a. track a fast ball with your eyes by watching the ball; b. get comfortable against fast bowling. Make sure you are protected as well - wear a chest guard or an arm guard if you are new to Bola or high speed machine bowling. Bola hurts! [Note: When drilling shots or "grooving", use Bola between 62-68 mph. Those are different drills and not to be confused with what I am suggesting above.]
2. Net against as many different types of bowlers as you can. Initially, you will get bowled or even edge out but don't fret. Keep going at it until you become comfortable.
3. Develop your technique and this will take time. Coach can be a tremendous help with developing your technique. If you live in the UK, then you have a lot of options. Check out CricketYard on Youtube. It has some tips from ABD. One of his tips solved a huge problem I had with my trigger and preparation.
4. Sometimes best you can do against a quick is survive and not get out. Scoring runs or hitting bigs shots is not always possible against good, quick bowlers. Try to save your wicket and see them off. Last season, I opened against a quick who used to play first class cricket in the West Indies. When was I walking to bat (wearing a helmet), some Graham Norton wanna be yelled from the first slip: "Are you wearing a helmet?" In a few minutes, I knew what he meant.

I didn't hit a single boundary against that guy but I took lot of singles and saw his 5 overs off. You can tell they (bowlers) are getting tired after every over. I had much better scoring matches than that one but that was the highlight of my season - I saw off a genuine quick bowler who had 4-5 variations in his repertoire.
Good luck.