The feelings you express are actually quite common ones among spiritual seekers. Because of specific events, or as a result of continued difficulties, struggles, and failures over time, people begin to feel that they are not good enough, or strong enough, or committed enough, or free enough to succeed in the spiritual ascent upon which they had embarked.
People are naturally disappointed when they don't get fast relief from deep problems that trouble them greatly. But the truth is, many problems ARE stubborn, and die hard. On top of that, people are their own worst critics. Therefore, under such conditions it is easy for people who are striving to become frustrated, to reach a point of diminishing returns, and to become discouraged with their track record.
Furthermore, most people are not consistent in practice. While they may invest considerable effort trying to overcome certain problems, they may also, at the same time, spend a lot of their energy hanging on to those same problems, and perhaps even aggravating them. For example: A person who tends to be resentful may have a bad habit of actually building cases against others inwardly. And yet, the indulgence of negative tendencies is another big reason why, oftentimes, the path of spiritual progress can seem so very slow, long, arduous, and ineffective.
The solution is not to fault yourself, or to fault the tools that seemed to have failed you. Remember, you had certain flaws going in -- if you had felt you were perfect, you may not have felt the need for spiritual practice in the first place! You tried to correct certain flaws, but were not entirely successful -- YET. If it's any comfort, think about it this way: If enlightenment were easy, the masses would be enlightened!
Perhaps the best approach would be to strive to hold your past experiences and your remaining challenges as constructively as possible. An optimum combination of persistence, faith, and constructiveness is required to make rapid spiritual progress. So, now it's a question of, "Can I hold things differently? Can I sufficiently correct some of those character flaws I've discovered, to be able to succeed where I have stumbled in the past?"
Surely, the answer is yes.