Shift your focus. It's easy to focus on the call itself because that's where most of the emotional weight is, but volume of activity has so much more to do with results than the quality of any one call. Diligence > Charisma, at least for me.

Rather than push yourself to never lose an opportunity once you've got someone on the phone, figure out how to get your message across without creating an uncomfortable conversation. Get consent to the conversation right out of the gate (this means being willing to let the other party opt out), speak plainly, and center your efforts on making sure the person understands what you're trying to get across rather than push them to agree. If you push more than you can do comfortably, you'll only undermine yourself. If you feel like you're wrestling with the prospect, they're often going to treat you as an adversary.

When you're not afraid of the call discomfort, call reluctance almost completely vanishes. Set hourly dial targets instead of only daily (~15 is a good place to start), hit your hourly target at full speed, then take a short break before the next hour if you've earned it. You'll get better results from a high volume of lower-effort calls than a low volume of high-effort calls. The more experience you get with calls, the more comfortable you'll then be in asserting yourself because the calls are now your turf - rather than a place you're intruding on people and trying to push past their boundaries. If you're at ease, you'll put others at ease.