i really think both running and exercising at the gym is good for your body and your soul!
running after a hard and stressful day with meetings, presentations etc...is really relieving! during the first ten minutes you still keep on thinking about things you've done at work, things you have to do and so on...and (so it is to me at least) sometimes you really get good ideas! after a while your thoughts about work fade away and you just enjoy running over the fields, running through the woods, breathe fresh air and everything. after you get back you're really relaxed and chilled...and, of course, a bit tired or exhausted (depending on how long and fast you run...). drink lots of water afterwards, eat lots of carbs afterwards (pasta or rice is best) and then just relax! (and don't go running with an empty stomach, eat a banana or something similar before, but no later than one hour prior to departure!).
maybe i should add here that i run regularly and that i've already run a marathon. so when it gets to competitions, you really have to take things serious. but even if you go running for half an hour or an hour, it's really a good thing! sometimes when weather is crap outside you really have to push yourself to put your running shoes on and get off your sofa. but then, after about 10 minutes of running through the rain, you'll love it. you don't care anymore that you're totally wet. just make sure you wear the right clothes (breathable stuff). the hot shower after your run is just perfect, and when you make an ice-cold-shocker at the end, you will stay warm for the next 12 hours. and don't forget stretching after getting back...i easily spend 20 mins for stretching!
as for gym, it's the same feeling after a stressful day. two things are different: you don't get that nature feeling (which is a bit sad) but on the other hand, if you exercise often, you will really see results in the way your body changes
i do sports 3-5 times per week and it's no problem (sometimes i can't make it because i don't have the time to), just look that your body gets enough recreation between the workouts! your body will need more sleep than before, but i swear you will feel better and healthier.
more questions? just ask!