I don’t think there is an “inyan” for this, as in a source in Torah literature etc. However, it is a valid point. It is a good thing to focus on one thing at a time, otherwise you’ll never experience anything. Imagine in a few years you’re leaning back on your recliner and taking in past experiences in your life. You’ll want to know that you lived the happy times to their fullest, and the sad times too. This way it might just be all muddled.
