@Truth1253 and @joncooper1986, I was exactly the same. Trust me, it will go away quickly. A few more tips:
For your first few times asking focus on yards that have spotty/dead/weedy lawns, but are still short/recently mowed. These are the easiest yes's. Once you get comfortable and confident with asking, then you can start thinking about nicer yards. Most of my no's have come from neatly manicured lawns, so I typically avoid them unless it is a super juicy old property. In that case, I will wait until fall or winter to ask, when the lawn is dormant or has some leaf fall.
My favorite areas are streets that are full of old properties. You can use this to your advantage. For example, you can add in a "I was just detecting at your neighbor So and So's yard" in the mix. It just adds another layer of comfort for the homeowner to steer them to a yes.
There will be a bunch of homes where no one will answer the door simply because they think your will be selling something. Don't let that discourage you, move on to the next.
I can't tell you how many times I've had really friendly homeowners that invite me to detect their backyards or we'll have a great conversation about the history of their home or neighborhood. I've found that people generally love to talk about the history of their homes. For this reason I have the Zillow ap on my phone. You can GPS your location and see when the home was built and any major remodels. Many homeowners will be impressed that you know when the home was built and many don't know themselves. This kind of conversation is usually a good segway into gaining knowledge of a neighborhood or area. I'll ask "if you were a detectorist, where would you go?" and they'll say "oh you should definitely ask Mrs. So and So because she owns the field that used to host community sales a long time ago", for example.
Last, look for those old cracky sidewalks that have lawns that are sunken below sidewalk level. This is a good indicator that they have not been filled. If the base of the lawn is high up or mounded above the sidewalk, this is a good indicator that it has been filled and that old targets could be too deep. Prioritize! Good luck dudes!