2) GIFTS Your best friend gave you a vase for your wedding...your grandma left you a table when she passed on. It's not your style but you are concerned that if you don't keep it it makes a disrespectful statement. NOT SO. We all get items from people that we love and respect. The true meaning of the gift was to celebrate an event in your life or to honor a memory. The item shouldn't be associated with the memory. Your duty is to receive the gift and thank the giver...not to keep it forever. The solution is to give/donate it to someone else who will continue to enjoy it.
3) FUTURE VALUE Worrying that something you have kept will be valuable again is very common. The internet can be a great source for finding its value. Check eBay, do a Google search, or even find an appraiser. For items that are valuable, consider having a professional appraisal...often done at no charge when an item is sold through them. It's worth knowing that toys, figurines, etc... NEED to be original packaging and in pristine condition to be worth selling.
5) MULTIPLES Having many of one item (this applies to clothing, accessories, costume jewelry, suitcases... everything!) that you don't use but "may need one day" is normal. However, when they overload your cabinets, closets, and garage they become obstacles. You fear that they may be useful 'down the road'. Aha..since you have NOT used them, take them from the space, put them into a bin and store them elsewhere. If in six months (or a year if you need it) you still haven't used them, bring that bin to a local donation donation. You didn't miss them, and it's likely you never will!
If your desire to de-clutter is hindered by time and motivation, take baby steps. Rather than tackle the whole closet, garage, etc... in one day, pick a corner, and complete just that area. Keep bins with easy to read labels "KEEP", "DONATE", "DISCARD" , "RECYCLE" and when the bin is full - take care of it. As your spaces become clean and neat, your treat will be to dress them up as you like!