It's the ones we have with those we love; those who matter most in our lives. It's the conversations that will either strengthen, damage or break bonds; but they are necessary. Our pride can convince us at times we don't "need" to have a difficult conversation with someone we love because we feel "they should already know" or "I shouldn't have to say x,y,z".
Fear often instigates the problem too. Making it hard for some to broach certain subjects while others simply cringe at the thought of tough conversations because it requires confrontation, and on some levels it requires vulnerability.
Relationships (friendships included) are never easy because you're consistently tested in areas the relationship is weakest: communication, honesty, loyalty, even consideration for one another. Consideration is probably the second most difficulty in relationships behind communication because it employs some level of sacrifice on our part for the one we're involved with. To consider someone is to think of them or do for them without them asking. It calls for us to be proactive for those we love. Our actions are for their benefit.
With respect to romantic relationships the tests, generally, surface during the dating or courting phase which many of us skip because we have a tendency to bypass that stage and go straight to the relationship in haste. The relationship "glitches" that we experience dwell in the "getting to know you" phase; there's no way to avoid them. That's when the "snags" reveal themselves. If we pass by that stage, we miss those learning scenarios and opportunities. They are the sneak preview of what we'll need to work on (with that person) if/when things graduate to a relationship. There's no point in moving forward to a relationship if you can't resolve things while dating. When we afford ourselves the opportunity to court we get the privilege of a practice test (so to speak) with that person.
Don't get distracted by the kinks. Work through them when it's worth it....
Follow me on Twitter@therealcstewart