Here's another entry from the Greg Marquez Commentary on scripture.
The love of God, not the love for God, is shed abroad in our hearts. This is a regular theme of Paul's. We are a new man, a new creature, made in the likeness of God. Part of that new creation includes God's very own love. We have God's love in our heart. That is why Paul does not set us up a bunch of rules telling us how we should live or walk. We don't need rules for walking in love we have God's love in us. What we need is to let God's love rule in our lives.
The rest of the scripture seems to make very little sense. It's difficult to understand a direct connection between "not ashamed" and God's love being shed abroad in our hearts. As a result some modern translations have translated, "not ashamed" as "does not disappoint". Which still doesn't make much sense if you're expecting a logical connection between, "does not disappoint" and the love of God being shed abroad in our hearts.
I think if we look at the context though we can see what Paul is saying, and it's pretty powerful stuff. First let's look at the phrase, "not ashamed'. which according to Thayer's consists of two words: