Action

Count your calls.

Explanation

If you don't get enough leads from other sources, you have to make cold telephone calls. Rejection is the pain one wants to avoid. Hit rate is everything. Improvement depends measurement.
Another thing. If you know your ratios, i.e. 20 calls:5 appointments:1 sale, you know how much you get paid for just picking up the telephone.

Method

Put crosses on a grid or ticks on a sheet. Categorise your calls to identify the difference between a miss (when you don't speak to anyone or get any useful information), a partial hit (when you do get some useful information), and a hit, (when you get an appointment, booking, or whatever you define).

Result

Your hit rate will continue to improve as long as you continue to focus on improving it. This will have a direct effect of increasing your sales. 
If you improve your ration from 30:1 to 25:1 you will sell 20% more.