This is something that I had to correct in myself. Before, even when I understood that most tasks that I was not delegating out right away were weighing on my already pretty full queue, I still had a hard time letting someone else take control. I knew this had to change and here is what I did to achieve it:
First thing I did was ask myself why I behaved that way.
After a bit of self-digging I came to realize it was difficult for me to accept the costs associated with delegation of tasks. In other words, I was trying to save money by not delegating.
So I did a number of exercises that helped me slowly start letting go of the money aspect of it. What I saw was an increase in the cash flow that could easily cover the expenses incurred. Turned out, paying for third party services changed from big hairy monster into profit increasing machine. The tasks that weighed me down for months at a time started dissipating. A sense of accomplishment and fulfillment grew with each completed task, which has got to send a positive wave into everything else in your life.
So here is the summative generic version of the advice that I can give based on my personal experience: work on shifting your perspective towards delegation by working on the mental block that is stopping you from letting go of control (for me it was associated with money), and I promise you, it is going to feel amazing once you get there
Best of luck on your journey, loves!