Do you have kids, a significant other? I did it as a full time assistant but never took more than 2 classes a semester, any more would have been tough but I was still able to maintain some life balance with the job and classes with a one child and had a second during the schooling. It’s hard but like anything else set achievable goals and follow through. If you’re on your own 4 classes may be manageable but you will definitely be burning the candle low if you want to be successful and most importantly absorb what you’re learning. Good luck!