If positive reinforcement via words of encouragement is your "love language," then use them often.
Put a stop to the self-criticism and give yourself some credit. Motivate yourself by telling yourself positive things like "You're doing your best" or "I'm proud of you."
Spending time with someone means more if you pay attention to them the whole time. The meaning of this is obvious while you're in a relationship, but it's all about you when you're single.
Join a gym and work out by yourself. Pay attention to the here and now. Find ways to relax and enjoy being by yourself.
Someone who appreciates a spouse who does something for them, especially when they don't have to, would likely appreciate an act of service.
Clean up the kitchen, put away the clothes, and mop the floor. Put together some nutritious meals for yourself. Spend some time and energy making your room comfortable and inviting.
Those that give gifts are ones who appreciate the time and care that goes into finding something special for someone else. Invest on something nice for yourself if you can afford it
Be serious about your own future and financial security by investing in your education. Make a plan for the vacation you've been dreaming of taking.
Holding hands, giving a hug, rubbing someone on the back, etc., are all examples of physical contact that may be extremely comforting and soothing in a relationship.
Maybe you could give yourself a day at the spa, where a trained therapist will massage your muscles and give you the flawless facial you've been craving.