I've found that when I'm down, in a rut, or tired, doing simple acts of good is one way to help me feel better. I occasionally make donations to GiveWell (on top of my monthly donation) or set up blood donation appointments (effective insofar as it comes out of the time I would spend reading at home, but instead read while giving blood). Are there are activities like these that are low effort but have high emotional payoff for me and reasonably high altruistic payoff for others?
This is a bit of a frame challenge, but I think it's OK to feed stray cats. Most people are built to empathize with people around us, not the total sum of global utility, so it's hard to beat the emotional high of a simple random act of kindness. (Conversely, for most people, the vast majority of good you can do comes from your career choice, and it's hard to approach this with small-scale actions.) So my advice is to pick someone close to you, do something nice for them and not worry about the magnitude of the altruistic payoff. You could also reflect on the positive long-term impact of some action (mentally follow the chain all the way from "finish project" -> "gain career capital" -> "get hired by <EA org>" -> "be able to work on <cause area>" -> reduce suffering) and use that to motivate yourself, but that only works for some people.
This is a classic idea in EA circles going back to 2009, and it absolutely still applies.
In the spirit of Aaron Gertler's expansion on calling elderly relatives, we can extend "feeding stray cats" to spending time with animals. This can be as small as giving some extra attention to local animals--in my case, I like to hang out with the cows and sheep at my university who are destined to become meat--or as significant as volunteering at a farm sanctuary.