Your instructors comments sound harsh, but I'm reluctant to criticise, as they might just be being honest with you.
In addition to the above advice, I've something else for you.
After I got my PPL, I started to use a GPS. Initially I didn't look at it on every flight....for some I just did things the way that I was thought, and just left the GPS running where I could get at it if I really needed too.
Now this produced something that was really unexpected for me. The GPS recorded breadcrumbs....a trail of points showing exactly where you were at each second. Looking back on flights, and comparing it to my plog notes, I realised that many of the 'wind corrections' that I made, were nothing to do with wind, but small errors that multiplied over legs.
For example, on many occasions I turned 1 nm too early. It's the difference between turning when you're over the town, and when you're over the town centre. It sounds like nothing, if it multiplies over two legs, it can lead to a noticeable difference. If you interpret that as a change from planned wind, and now make corrections for it, it can really mess things up and the mistakes multiply.
I only noticed this from being able to look at the GPS trail afterwards. Most times the mistake is not on the leg on which you get lost on, but the previous one or even the previous two. This is clear from the breadcrumbs, but hard to spot otherwise.
So I'd suggest that you ask your instructor to record future flights on a GPS (or you do it on your phone/iPad). Don't look at it in flight, as that's no use to you, but use it as a debriefing too afterwards. If you get lost, you can see where it all started to go wrong. If you don't get lost, you can see look to see if all your wind corrections where really wind, or a result of little mistakes.
If neither you nor your instructor have access to a GPS, then send me a pm, and I might be able to help.
One thing that I learned from this, as that the fewer turning points you have, the fewer opportunities there are for mistakes. So it can be better to fly a straight line, noting towns/places that you pass abeam, rather than trying to fly over them and then turn 5 degrees. For example, if you plan to fly from place A to place B, then turn 5 degrees, then fly to place C, you might be better off flying directly from place A to place C, and just note the time that you will pass abeam place B (which you'll still be able to see).
The other thing is that big obvious waypoints that can be seen from far away (lakes, large towns) make much better waypoints than small villages. They are much easier to see if you end up a few miles off tracks.
dp