Instead of trying to learn to knit a sweater in a weekend, sign up for a six-week class to learn the basics, then work toward your goal from there. Giving yourself a more reasonable amount of time to complete a task makes it less overwhelming.
Break a big task into smaller ones
Segmenting large projects into manageable parts makes them easier to accomplish. For example, if your long-term goal is to organize all your photos into online or physical albums, make a list of all the tasks required. Estimate the time each will take and block out the tasks as appointments on your calendar. As you complete each appointment with yourself, you'll feel more motivated to continue!
Sometimes you have to acknowledge that a project isn't worth the anxiety. If you're hanging on out of guilt, find a new goal or pursuit you really care about that will be worth your valuable time.