When I take strong stims, sometimes I'll get a feeling of approaching dread. It might be something I forgot, it might be a nebulous insecurity that my unadulterated mind keeps buried or isn't concerned with because it truly is unimportant. The key for me is to understand that the anxiety is a side effect of the stim...usually taking 15 seconds to consider the true cause of these feelings (stims) is enough to make the gloominess pass. If your emotional sides are more debilitating than that, I think I would try another stim.
Considering it sounds like you're building a tolerance to the stims, it sounds like you should cycle off for a bit anyway. I think that when you up your dose to maintain a certain level of desired effects, you're still opening yourself up to more possible sides and the risk/reward profile becomes less appealing.