All sin is like ink- black, damaging and permanent. Granted, some don't seem to regret their actions as much as others, but we all have stains on our souls in one way or another. It's much easier to try to point fingers and measure the width and breadth of other's sins, but truly that is not the point.
The point is that you can't separate human nature from human nature; the determining factor is how we change when we make a mistake. Obviously you can't take back your mistakes, but what do you do as your (so to speak) "morning-after" step two? Let the flames of self-hatred smother you? Play the blame game? Drown out the sound of your conscience by listening eagerly to monologues of self-pity and what-ifs?
Sinning doesn't make you an infidel; staying the same or getting worse afterwards does. The true test of character is how one lives the majority of his life, especially after committing a sin. If sin is poison, good works are pure, clean water: the more of them one does after repenting and asking God for forgiveness, the more the recently-injected poison is diluted. The dilution increases with the good works, and pretty soon, the ratio of poison to water is so great that one can barely tell the difference between pure water and sinner-gone-home water.
In the Bible, there are countless figures who start out committing terrible sins and/or living filthy lifestyles, but then repent and turn to God, only to become great people who make enormous, positive differences in the world around them.
If you fall and stub your toe, feel the pain of the injury, promise yourself to be more careful next time and maybe even get some new shoes. Then, get back up and keep the promise. It's all you can do.