Here's a thought experiment:
I'm going to tell you something, something exciting and long wished for: you're going to learn how to fly through the air without aid. OK? So what the plan is, is you're going to spend the next six months building your upper body muscles. You're going to need to hire a trainer who's going to work with you 4 times a week. It's going to be painful but you'll get the muscles you need. Then you are going to practice just jumping off objects, progressively higher. Then you're going to spend an hour a day flapping your arms. Finally, you're going to go to a high cliff, jump off, and with all your training, you'll fly! That's all there is to it, so the process should be easy and straightforward.
Now, let's say that you really want to fly, and that you may have deep faith in your mentor/trainer and really want to believe you can do it. There is a great desire. But underneath, to varying degrees hidden, there is a fundamental disbelief (right in this case, but play along) in either your ability to fly, or the possibility of humans to fly unaided. So while you try diligently to move forward with the protocol--you hire the trainer, you stand on your lawn diligently flapping--you notice you're not fully engaged, not seeming to do the training in a full-bodied (as it were) way. You skip days. You make excuses. You only jump from four feet when the schedule clearly calls for eight.
What's going on here? Basically, you are trying to mesh two injunctions: do it (because I need to, have to, want to please my Mentor, etc.) and don't do it (because it's impossibly, I'm not worthy, I'll die). While the "do it" voice may be louder or more obvious-it's what you tell yourself and others-the "don't do it" is the more powerful because trying to do what you believe is impossible is at root felt as a threat to survival or the opening to overwhelming pain. While one foot is on the gas, your hand is yanking on the hand brake in an effort to stop what is felt as a dangerous acceleration towards a cliff.
In the case of flying like this, your survival mechanisms are actually right. But in many, many more cases, especially for people suffering from anxiety and depression, beliefs are outdated at best, related to times past which are no longer relevant to the present. "I need to be small to be safe," would be skillful for a child in a dangerous family. But when the belief persists on into adulthood, it's no longer protection, but rather enprisonment.
But beliefs are tenacious. They can't be muscled through, or lept over, or swept under the rug. They only change by seeing through or contradicting their own logic, but not like winning a debate. Beliefs shift in the face of new, credible information and experiences.
Easy to say, but tricky to do, in large part because most important beliefs, the ones that control the hand brake of one's life, are essentially beliefs about what's necessary for survive. "Don't express anger, because people will attack you and you have no defense." "Always tend to other's needs, because if you don't, they will abandon you and you can't support yourself."
These are rules of safety, with the basic assertion of "adhere or die." So, they're not given up easily, even in the face of devastating critique. We will rarely release a belief until we have something else to replace it, to provide a sense of safety. And until that need for safety is addressed, our survival beliefs will keep slowing us down.
In other words, when you find yourself dragging on a goal, avoid responding with either fighting or collapsing. Keep in mind that some governing belief has got it's hand on the brake, and slow down instead, putting your attention on what that belief might be and how to reassure your deep self that you can (or how you can) move forward and be safe. When that part of you is convinced, then effort is easy.
And in this process, the more supports you have, the better. (Click here for more thoughts on this.) With the flying training, if you had somewhere safe to land, people applauding your efforts and telling you that they love you even if you fail, wouldn't you be much more likely to risk the final flying test?
Having supports to lean on in the process of changing beliefs is essential, because otherwise your hand brake part will override the gas pedal part of yourself, and you'll just create a lot of heat and smoke.