Thor - you seem to have a great attitude, and that is really all you need in training. If you want to be there and don't forget that you want to be there, you will have no problems. None of the training - Marine officer, or aviation training - is impossible. It will be a rewarding experience if you appreciate it when it is challenging, and stay focused and driven when it is not (because sometimes waiting for the word at TBS, cleaning your weapon at OCS, and chair flying in primary are not the most exciting things in the world). The best things I can tell you - study like crazy for the flight test if you have not already taken it. Go Marine. You will never regret it. Get a flight contract, because they are hard to come by out of TBS. Prepare yourself for the weather at OCS. It's hot and humid in the summer, and cold enough to bother you in the winter, because you are outside most of the time. Run in boots. And stay motivated. It's all very simple if you maintain your focus. People want jets, but don't get them because they don't want to study as much as they know they should. Others have great grades, but bad timing. No one can promise you anything, so be prepared to work for want you want, and to be happy with what you get. That attitude will make your journey the most fulfilling.
Good luck.