Big problems don't go away overnight.
If you learn a friend is struggling with a significant problem, they'll probably still be struggling down the road. Help them out by remembering to check in.
For instance, if your friend shares a struggle they're having, it might be appropriate to text them the next day to say “Hey, I'm thinking of you and I'm behind you 100%” or call them a few days later to invite them to coffee.
If you know a friend is having a hard time in general (maybe they are struggling with depression or recovering from a breakup), be deliberate to occasionally ask them how they are doing – and stick around to hear the real answer. People will often withdraw from social interaction when they are depressed, so reach out to them if you haven't seen them for awhile.
Remember, your friend might be in so much pain that they don't want to talk about their problem. I know that when I am going through a breakup, the last thing I want to do is talk about it – the pain is still too raw.
If they don't want to talk about it, provide them with some positive interactions that aren't focused around their problem. Invite them to hang out with you at the mall, or see a movie together, or go for a run. Basically, invite them to remember the good parts of life, and give them a respite from brooding over their loss.
It's possible they won't want to do any of these things – sometimes when you are suffering, you can't enjoy normal activities. But even if they say no, it helps to know that you cared enough to ask.
It makes a huge difference to have a friend care enough to check in. Don't let your friend drop off the radar. If you know they're struggling, follow up on a regular basis and make sure they know you care about them. Invite them to coffee. Let them know you care. Give them a call.
They'll be glad you did.
Next: Don't insist