There is one thing that can really make a difference in your day: how well you slept the night before.
Cut corners on other things so you can have a better bed. A good mattress is a truly wise investment.
No matter your mattress, though, what you really need is enough time spent with it. Get to bed at a reasonable hour, get a good night's rest, stretch when you get up in the morning, and then face the world with a bit more (bed)spring in your step.