As you saw by yourself, RE is not a easy skill to accomplish. One must find as much patience (at least) as he could to acquire it, some intelligence and knowledge will also help. If you think that just following the tutorial you will understand all of it from the first read, then you are wrong.
My advice to you is :
- read the tutorial several times and try to pass it without looking into the writings
- try to understand as much as you can about OS/platform you are reversing on
- be proficient with PE format for a start or the file format you are dealing with
- read about packers and obfuscation techniques
After that, I'm pretty sure, if you come back to that tut again, you will understand it more clearly.
Here are some good resources:
- Malware Unpacking In Ollydbg
- Finding OEP and unpacking Malware packed with ASPACK 2.12 - try it although you said, you came across similar ones
- Fravia's archive pages of reverse engineering
- Overview of PE file format
May the force be with you :)