Constant demands and time pressures slowly wear you down, so it's important to detach yourself and give your mind (and body) some well deserved rest every now and then.
No matter how busy you are, how critical your role, how many lives are depending on you - you can't give 100%, 100% of the time. By stretching yourself too thin, you open the door to mistakes, lapses of judgment and other issues associated with exhaustion.
Better to take a break now, during the summer (when everyone else is also in low gear) than risk 'running out of steam' or facing a health issue when things are really busy.