I know all too well about the mental block phase. I am in the process of de-cluttering also and ridding of the sentimental items that we really do not use, but for only keepsake. I have even been called a miser for all my collected items. lol.
If getting mentally blocked while in the cleaning process, I just give myself a break and get a change of scenery. IE go to the best room/ area of your house that is a clutter free zone. From this spacious/ clutter free area, you'd get motivation to execute the same spacious room for the clutterbox room.
I have often "put- off" /avoided organizing myself and it can seem like the room would be shrinking for each minute more that you spend in there, hence the mental block. Just maintain focus, take interval breaks, make "sectioned goals" for each part of the room and do this for at least; once EVERY WEEK and slowly but surely, you'll see the clutter retreat and eventually disappear.
GL