Practical limits are built into 'effective'. The most effective activity for you to engage in is the most effective activity for you to engage in, not for a perfectly rational arbitrarily computationally powerful god to engage in. Going easy on yourself, to the optimal degree, is (for creatures like us) part of behaving optimally at all. If your choice (foreseeably) burns you out, and the burnout isn't worth the gain, your choice was just wrong.