Trust me I'm trying, I'm saving up as much money as I can for a hunt but walking dogs isn't going to get me far in paying for an African hunt, sitting on 7 grand some are in stocks, silver, gold etc. but I'm not willing to blow it all away. Going to college at 18 hopefully becoming a petroleum engineer at 20-22 depending on getting a masters or not, but then once I get a job after taxes, insurance, and finding a house I probably won't be able to have significant money left over until 30. Let's hope hunting can hold out until then and even afterwards, I'll always hold out hope for the future but I'm sure the hunting in heavens better anyway.
I'm in pretty much the same boat, if a little further along. Currently just out of uni in my first job, buying a house sometimes this year with a decent portfolio of investments which I'm currently unwilling to spend.
Main thing is focus, as has been said. You're choosing a good degree with decent earning potential, now it's up to you. Get to the right Uni, get a first class degree, get a good job. After that it's a walk in the park (I'm told)...
In the mean time, you have to be pragmatic about it. I get to hunt a fair bit at the moment, even on a small budget, but you have to pick your hunts. Ask yourself, will you get more enjoyment out of that perfect DG hunt in 25 years time, or would you rather take a decent PG package in 5? Having done a limited amount of 'trophy' hunting and a lot more 'cull' trips, I can say that I at least get just as much enjoyment out of a day in the field after cull hinds as I do after a top quality stag. Can't imagine Africa would be any different. Plus, I can take 10 days on hinds for the price of one on stags. I'm in a position where I could potentially take a fortnight for a budget plains game hunt, or some driven boar etc, but DG? Unlikely.
My advice is take what you can when you can and be happy about it. If your budget only stretches to bunnies, then no bother. I spent many happy years blatting bunnies. Most people get economically better off as they get a bit older, but to miss out on a world of trips in pursuit of that One Perfect Trip may not be entirely wise, especially when, as you say, there's a chance that external forces may prevent it from ever materialising. Build up to it, enjoy what you can in the interim and be comforted that, in my opinion, it's almost guaranteed that there will be at least a few places where you can take the Big Five throughout our lifetime, it just depends on the cost you have to pay and if you feel that it's justifiable in light of whatever the population density is at that precise moment.
A final thought. A bit of your investment in the interim in terms of PG hunts in these areas will greatly increase the chance of DG oppurtunities still being available when you are in a position to take them. It's a win win!